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A Comparison of Source Types and Their Impacts on Acoustical Metrics

Permanent Link: http://ufdc.ufl.edu/UFE0044693/00001

Material Information

Title: A Comparison of Source Types and Their Impacts on Acoustical Metrics
Physical Description: 1 online resource (149 p.)
Language: english
Creator: Siebein, Keely Moreen
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2012

Subjects

Subjects / Keywords: acoustics -- architectural -- clarity -- directional -- edt -- natural -- omnidirectional -- reverberation -- sources -- standards
Architecture -- Dissertations, Academic -- UF
Genre: Architecture thesis, M.S.A.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The purpose of this study is to compare acoustical measurements made with different source types in a relatively reverberant room to determine if ISO 3382 monaural acoustic parameters such as Reverberation Time (RT), Early Decay Time (EDT), and Clarity Index (C80), yield different results for natural acoustic source stimuli. The source stimuli used in the study included Maximum Length Sequences (MLS), a running train of speech, a running piece of music and a balloon pop. The scientifically calibrated method is then compared to acoustical measurements obtained from natural acoustic sources, which include anechoic recordings of voice and music played through a directional speaker in the front of the room to simulate activities that would normally take place in the room, such as a person speaking and music being played during a worship service. This analysis is performed to determine if there are differences in acoustic room parameters using natural acoustic sources. This study essentially compares the effects of different source stimuli on measured acoustic parameters. It was found that different source signals and receiver locations significantly affect the acoustic metrics derived from the acoustical measurements due to variations in frequency, level and directionality.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Keely Moreen Siebein.
Thesis: Thesis (M.S.A.S.)--University of Florida, 2012.
Local: Adviser: Gold, Martin A.
Local: Co-adviser: Siebein, Gary W.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2012
System ID: UFE0044693:00001

Permanent Link: http://ufdc.ufl.edu/UFE0044693/00001

Material Information

Title: A Comparison of Source Types and Their Impacts on Acoustical Metrics
Physical Description: 1 online resource (149 p.)
Language: english
Creator: Siebein, Keely Moreen
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2012

Subjects

Subjects / Keywords: acoustics -- architectural -- clarity -- directional -- edt -- natural -- omnidirectional -- reverberation -- sources -- standards
Architecture -- Dissertations, Academic -- UF
Genre: Architecture thesis, M.S.A.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The purpose of this study is to compare acoustical measurements made with different source types in a relatively reverberant room to determine if ISO 3382 monaural acoustic parameters such as Reverberation Time (RT), Early Decay Time (EDT), and Clarity Index (C80), yield different results for natural acoustic source stimuli. The source stimuli used in the study included Maximum Length Sequences (MLS), a running train of speech, a running piece of music and a balloon pop. The scientifically calibrated method is then compared to acoustical measurements obtained from natural acoustic sources, which include anechoic recordings of voice and music played through a directional speaker in the front of the room to simulate activities that would normally take place in the room, such as a person speaking and music being played during a worship service. This analysis is performed to determine if there are differences in acoustic room parameters using natural acoustic sources. This study essentially compares the effects of different source stimuli on measured acoustic parameters. It was found that different source signals and receiver locations significantly affect the acoustic metrics derived from the acoustical measurements due to variations in frequency, level and directionality.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Keely Moreen Siebein.
Thesis: Thesis (M.S.A.S.)--University of Florida, 2012.
Local: Adviser: Gold, Martin A.
Local: Co-adviser: Siebein, Gary W.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2012
System ID: UFE0044693:00001


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1 A COMPARISON OF SOURCE TYPES AND THEIR IMPACTS ON ACOUSTICAL METRICS By KEELY SIEBEIN A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN ARCHITECTURAL STUDIES UNIVERSITY OF FLORIDA 2012

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2 2012 Keely Siebein

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3 To my parents

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4 ACKNOWLEDGMENTS I would like to thank my mother, father, sisters, brothers, nephews and the rest of my family for all your love and support throughout my life. I would like to thank Professors Gold and Siebein for your continuous support, guidance and encouragement throu fellow acoustics students, Sang Bong, and Sang Bum, Cory, Adam B, Adam G., Jose, Jorge and Jenn and any others who helped me with the data collection and reviewing of the material and for keeping m support throughout this entire process, for believing in me and doing all that you could frie nds, for believing in me and encouraging me throughout my studies T hanks to my honor to have studied with you and learned from you in this capacity and I will treasure t hese years and the time I spent learning under your guidance forever. Thank you all for everything.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF TABLES ................................ ................................ ................................ ............ 7 LIST OF FIGURES ................................ ................................ ................................ .......... 8 ABSTRACT ................................ ................................ ................................ ................... 15 CHAPTER 1 INTRODUCTION ................................ ................................ ................................ .... 17 2 LITERATURE REVIEW ................................ ................................ .......................... 19 Architec tural Acoustics ................................ ................................ ............................ 19 Fine Structure of Reverberation ................................ ................................ .............. 22 Impulse Response ................................ ................................ ................................ .. 24 Overview ................................ ................................ ................................ .......... 24 Comparison of the Early and Late Portions of the Impulse Response. ............ 26 Acoustical Criteria ................................ ................................ ................................ ... 29 Reverberation ................................ ................................ ................................ ... 29 Early Decay Time ................................ ................................ ............................. 30 Clarity/Intelligibility ................................ ................................ ............................ 30 Diffuse Sound Field ................................ ................................ .......................... 32 Soundscape Theory ................................ ................................ ................................ 33 Worship Space Acoustics ................................ ................................ ....................... 36 Performance Space Acoustics ................................ ................................ ................ 37 Balloon Pop Study ................................ ................................ ................................ .. 38 Omnidirectional Speaker Study ................................ ................................ .............. 38 Directivity of Sources ................................ ................................ .............................. 39 Reverberation Time: Traditional Equations and Acoustical Standards ................... 41 Traditional Equations ................................ ................................ ........................ 41 Acoustical Standards ................................ ................................ ........................ 43 ISO 3382 ................................ ................................ ................................ .... 43 ASTM E 2235 ................................ ................................ ............................. 44 Just Noticeable Differences in Acoustical Metrics ................................ ................... 45 Reverberation Time ................................ ................................ .......................... 45 Early Decay Time ................................ ................................ ............................. 46 Clarity (C 80 ) ................................ ................................ ................................ ....... 47 3 ACOUSTIC SOURCE COMPARISON STUDIES ................................ ................... 49 General Information ................................ ................................ ................................ 49 Floor Plan ................................ ................................ ................................ ............... 49

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6 Reverberation ................................ ................................ ................................ ......... 49 Materials ................................ ................................ ................................ ................. 50 Pilot Study ................................ ................................ ................................ ............... 50 Method ................................ ................................ ................................ ............. 51 Electronic Signal Results ................................ ................................ .................. 51 Natural Acoustic Signals ................................ ................................ ................... 54 Anechoic voice and music as measurement sources ................................ 55 Live music as a measurement source ................................ ........................ 55 Balloon pop as a measurement source ................................ ...................... 56 Results ................................ ................................ ................................ ............. 56 Pilot Study Conclusions ................................ ................................ .................... 58 Source Signal Comparison ................................ ................................ ..................... 59 Method ................................ ................................ ................................ ............. 59 Study 1: Omnidirectional, Directional and Calculated Comparisons ................. 60 Electronic signals ................................ ................................ ....................... 61 Reverberation time ................................ ................................ ..................... 61 Clarity (C 80 ) ................................ ................................ ................................ 65 Study 2: Anechoic Music and Speech and Balloon Pop Stimuli Comparison ... 68 RT Comparison ................................ ................................ ................................ 76 RT EDT Comparison ................................ ................................ ..................... 78 Natural acoustic sources ................................ ................................ ............ 78 Scientifically calibrated sources ................................ ................................ 88 Reverberation Time Comparison Results ................................ ......................... 89 Early Decay Time Comparison Results ................................ ............................ 96 C 80 Comparison Results ................................ ................................ ................. 102 Just Noticeable Differences ................................ ................................ ............ 106 Reverberation time just noticeable differences ................................ ........ 107 Early decay time just noticeable differences ................................ ............ 109 Clarity (C 80 ) just noticeable differences ................................ .................... 112 Discussion ................................ ................................ ................................ ...... 115 Conclusions ................................ ................................ ................................ .... 116 Future Studies ................................ ................................ ................................ 129 APPENDIX A IMPULSE RESPONSE PRINTOUTS FOR WIN MLS SOURCES ........................ 130 B OMNIDIRECTIONAL AND DIRECTIONAL LOUDSPEAKER COMPARISON ...... 140 LIST OF REFERENCES ................................ ................................ ............................. 146 BIOGRAPHICAL SKETCH ................................ ................................ .......................... 149

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7 LIST OF TABLES Table page 3 1 Just noticeable difference in reverberation time ranges grouped by method .... 107 3 2 Just noticeable difference in reverberation time ranges grouped by receiver position ................................ ................................ ................................ ............. 109 3 3 Just noticeable difference ranges for early decay time grouped by method ..... 110 3 4 Just noticeable difference ranges for early decay time grouped by receiver position ................................ ................................ ................................ ............. 111 3 5 C 80 just noticeable difference ranges grouped by method ................................ 113 3 6 C 80 just noticeable difference ranges grouped by receiver position .................. 114

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8 LIST OF FIGURES Figure page 2 1 Polar plot of the directionality of human voice in 500 and 4,000 Hertz octave bands. Credit: M. D. Egan, Architectural Acoustics p. 83 ................................ .. 39 2 2 Polar plot of the directionality of trumpet in 220, 480, 920, 1840 and 4,000 Hertz octave bands. Credit H. F. Olson, Music, Physics and Engineering p. 235 ................................ ................................ ................................ ..................... 40 2 3 Directivity patterns of medium and large balloons. Credit: P tynen et al., ............................... 40 2 4 Polar plot of JBL EON15 G2 in the 500, 1,000 and 4,000 Hertz frequencies showing 3. 6 and 9dB radii ................................ ................................ .............. 41 2 5 Polar plot of the Norsonic 276 loudspeaker, which was provided by the manufacturer as a comparable polar p lot to the Norsonic 223 loudspeaker. Credit: Nor276 Dodecahedron Loudspeaker [cited 12 July 2012] Available from http://www.norsonic.com/index.php?sideID=6962&ledd1=6981 ................. 42 3 1 Standard Deviation of Reverberation Times from all Scientifically Calibrated Signals ................................ ................................ ................................ ................ 52 3 2 Comparison of all scientifically calibrated Reverberation Time measurements .. 53 3 3 Middle frequency Reverberation Times for average scientifically calibrated source signals with 99% Confidence Interval ................................ ..................... 54 3 4 Floor plan of Baughman Center showing source and receiver locations ............ 56 3 5 Reverberation T imes for the anechoic speech, music, live music and Balloon Pop sources in receiver position 3 ................................ ................................ ...... 57 3 6 Reverberation Time s in the middle frequencies for all source types ................... 58 3 7 Floor plan of Baughman Center indicating source types and positi ons and receiver positions ................................ ................................ ................................ 60 3 8 Standard deviation of Reverberation Time for the omnidirectional and directional louds peaker in the 1 st receiver position ................................ ............. 62 3 9 Standard deviation of Reverberation Time for the omnidirectional and directional loudspeaker in the 2 nd receiver position ................................ ............ 62 3 10 Standard deviation of Reverberation Tim e for the omnidirectional and directional loudspeaker in the 3 rd receiver position ................................ ............. 63

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9 3 11 Average measured and calculat ed Reverberation Times for the Baughman Center ................................ ................................ ................................ ................. 64 3 12 Clarity (C 80 ) values measured at the first receiver position with omnidirectional and directional loudspeakers ................................ ..................... 65 3 13 Clarity (C 80 ) values measured at the second receiver position with omnidirectional and directional loudspeakers ................................ ..................... 66 3 14 Clarity (C 80 ) values measured at the third receiver position with omnidirectional and directional loudspeakers ................................ ..................... 67 3 15 Placement of cursors to derive acoustic metrics for the Traditional Method using the end note of the Trumpet Song at 1,000 Hertz as an example ............. 70 3 16 Placements of cursors to derive acoustical metrics from the Expanded Method ................................ ................................ ................................ ............... 71 3 17 End note of Trumpet Song with 1,000 Hertz octave filter applied to signal. Note the times, as they are used in the next step ................................ ............... 73 3 18 Cursor placement after filtering and listening to Trumpet Song stop chord. Note placement of cursors corresponds to times identified in Figure 3 17 ......... 74 3 19 New wav file made by clipping the top image between the Reflected Sound and Noise Floor cursors ................................ ................................ ..................... 75 3 20 The new wav file from Figure 3 19 was run through WinMLS software program and acoustic metrics derived from this wav file ................................ .... 76 3 21 Reverberation Time comparison for Pilot Study, Study 1 and Study 2 in the 500, 1000 and 4000 Hertz octave bands ................................ ............................ 77 3 22 Female Talker RT EDT analyzed using theTraditional Method ....................... 78 3 23 Female Talker RT EDT analyzed using the Expanded Method ....................... 79 3 24 Female Talker RT EDT analyzed using the Perceptual Method ...................... 80 3 25 Female Talker RT EDT analyzed using the Perceptual WinMLS Method ....... 80 3 26 Trumpet Song RT EDT analyzed using theTraditional Method ........................ 82 3 27 Trumpet Song RT EDT analyzed using the Expanded Method ....................... 82 3 28 Trumpet Song RT EDT analyzed using the Perceptual Method ...................... 83 3 29 Trumpet Song RT EDT an alyzed using the Perceptual WinMLS Method ........ 84

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10 3 30 Balloon Pop RT EDT analyzed using the Traditional Method .......................... 85 3 31 Balloon Pop RT EDT analyzed using the Expanded Method .......................... 85 3 32 Balloon Pop RT EDT analyzed using the Perceptual Method ......................... 86 3 33 Balloon Pop RT EDT analyzed using the Perceptual WinMLS Method ........... 87 3 34 Averaged MLS meas urements dervied from the directional loudspeaker subtracting EDT from RT at receiver locations R1, R2 and R3 ........................... 88 3 35 Averaged MLS measurements dervied from the omnidirectional loudspeaker subtracting EDT from RT at receiver locations R1, R2 and R3 ........................... 89 3 36 Female Talker and Trumpet Song Reverberation Times normalized to average MLS data ................................ ................................ .............................. 90 3 37 Balloon P op source graphs showing similar RT values across receiver positions and methods ................................ ................................ ........................ 91 3 38 Graphs of Female Talker Normali zed Reverberation Times using Expanded and Perceptual Methods, which result in similar values ................................ ..... 92 3 39 Graphs of Trumpet S ong Normalized Reverberation Times using Expanded and Perceptual Methods, which result in similar values ................................ ..... 92 3 40 Spectrograph of the Female Talker last syllable with concentration of sound energy in the 6,500 to 9,200 Hertz octave bands ................................ .............. 93 3 41 Spectrograph of the Trumpet Song end note The Trumpet Song has more concentrated sound energy in many frequencies than the Female Talker ......... 94 3 42 Spectrograph of the Balloon Pop. The solid decay of green, yellow, red and orange indicate very strong levels across all frequenci es ................................ ... 95 3 43 Female Talker source analyzed with Traditional, Perceptual and Perceptual WinMLS methods resulting in similar normalized EDT values ............................ 97 3 44 Female Talker Normalized EDT values for Receiver Positions 1 and 3 ............. 98 3 45 Trumpet Song Normalized EDT values for Traditional and Perceptual WinMLS methods ................................ ................................ ............................... 98 3 46 Trumpet Song Normalized EDT values for Expanded and Perceptual methods ................................ ................................ ................................ .............. 99 3 47 Graphs showing large variation in left and right receiver normalized EDT values for Trumpet Song compared to fairly consistent Female Talker values 100

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11 3 48 Graphs of Balloon Pop analyzed with Expanded and Perceptual methods resulting in similar normalized EDT values ................................ ....................... 101 3 49 Balloon Pop analyzed using the Perceptual WinMLS method resulting in EDT values that are centered around average MLS data ................................ ......... 101 3 50 Balloon Pop source at receiver positions 1 and 3, showing differences in left and right receivers as the receiver position moves farther from the source ...... 103 3 51 Graphs of Female Talker Normalized C 80 values using Expanded and Perceptual Methods, which result in similar values ................................ .......... 103 3 52 Graphs of Trumpet Song Normalized C 80 values using Expanded and Perceptual Methods, which result in similar values ................................ .......... 104 3 53 Graphs of normalized C80 values for Balloon Pop source for the 3 receiver positions ................................ ................................ ................................ ........... 105 3 54 Graphs showing Female Talker having similar JND values in the 4,000 Hertz octave band for Expanded and Perceptual methods ................................ ........ 108 3 55 Graphs showing Trumpet Song having similar JND values in the 4,000 Hertz octave band for Expanded and Perceptual methods ................................ ........ 108 3 56 Balloon Pop Expanded and Perceptual Methods showing similar Just Noticeable Differences in Early Decay Time ................................ .................... 111 3 57 Balloon Pop Perceptual WinMLS method showing low JND values for Early Decay Time ................................ ................................ ................................ ...... 112 3 58 Graphs showing Female Talker having similar JND values for C 80 across the octave bands for Expanded and Perceptual methods ................................ ...... 113 3 59 Graphs showing Trumpet Song having similar JND values for C 80 across the octave bands for Expanded and Perceptual methods ................................ ...... 114 3 60 Impulse response graphs of various sources used in study ............................. 119 3 61 Average RT EDT values for Female Talker source ................................ ....... 120 3 62 Average RT EDT values for Trumpet Song source ................................ ....... 121 3 63 Average RT EDT values for Trumpet Song source ................................ ....... 121 3 64 Average Normalized Reverberation Time for Female Talker source ................ 122 3 65 Average Normalized Reverberation Time for Trumpet Song source ................ 12 3 3 66 Average Normalized Reverberation Time for Balloon Pop source .................... 123

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12 3 67 Average Normalized Early Decay Time for Female Talker source ................... 124 3 68 Average Normalized Early Decay Time for Trumpet Song source ................... 124 3 69 Average Normalized Early Decay Time for B alloon Pop source ....................... 125 3 70 Average Normalized Clarity (C 80 ) for Female Talker source ............................. 125 3 71 Average Normalized Clarity (C 80 ) for Trumpet Song source ............................. 126 3 72 Average Normalized Clarity (C 80 ) for Balloon Pop source ................................ 126 3 73 ... 127 A 1 MLS Directional Front: Receiver 3_1 ................................ ................................ 130 A 2 MLS Directional Front: Receiver 3_2 ................................ ................................ 130 A 3 MLS Directional Front: Receiver 3_3 ................................ ................................ 130 A 4 MLS Directional Corner: Receiver 3_1 ................................ ............................. 130 A 5 MLS Directional Corner: Receiver 3_2 ................................ ............................. 131 A 6 MLS Directional Corner: Receiver 3_3 ................................ ............................. 131 A 7 Sine Sweep Directional Front: Receiver 3_1 ................................ .................... 131 A 8 Sine Sweep Directional Front: Receiver 3_2 ................................ .................... 131 A 9 Sine Sweep Directional Front: Receiver 3_3 ................................ .................... 132 A 10 Sine Sweep Directional Corner: Receiver 3_1 ................................ ................. 132 A 11 Sine Sweep Directional Corner: Receiver 3_2 ................................ ................. 132 A 12 Sine Sweep Directional Corner: Receiver 3_3 ................................ ................. 132 A 13 Multiple Sine Sweep Directional Front: Receiver 3_1 ................................ ....... 133 A 14 Multiple Sine Sweep Directional Front: Receiver 3_2 ................................ ....... 133 A 15 Multiple Sine Sweep Directional Front: Receiver 3_3 ................................ ....... 133 A 16 Multiple Sine Sweep Directional Corner: Receiver 3_1 ................................ .... 133 A 17 Multiple Sine Sweep Directional Corner: Receiver 3_2 ................................ .... 134 A 18 Multiple Sine Sweep Directional Corner: Receiver 3_3 ................................ .... 134

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13 A 19 Piano Middle C Note: 500 Hertz ................................ ................................ ...... 134 A 20 Piano Middle C Note: 1,000 Hertz ................................ ................................ ... 135 A 21 Piano Middle C Chord: 500 Hertz ................................ ................................ ..... 135 A 22 Piano Middle C Chord: 1,000 Hertz ................................ ................................ .. 136 A 23 Piano Song Stop Chord: 500 Hertz ................................ ................................ .. 136 A 24 Piano Song Stop Chord: 1,000 Hertz ................................ ............................... 137 A 25 Anechoic Trumpet Music: 500 Hertz ................................ ................................ 137 A 26 Anechoic Trumpet Music: 1,000 Hertz ................................ .............................. 138 A 27 Anechoic Female Talker: 500 Hertz ................................ ................................ 138 A 28 Anechoic Female Talker: 1,000 Hertz ................................ .............................. 139 B 1 MLS Directional Front: Receiver 1_1 ................................ ................................ 140 B 2 MLS Directional Front: Receiver 1_2 ................................ ................................ 140 B 3 MLS Directional Front: Receiver 1_3 ................................ ................................ 140 B 4 MLS Directional Front: Receiver 2_1 ................................ ................................ 140 B 5 MLS Directional Front: Receiver 2_2 ................................ ................................ 141 B 6 MLS Directional Front: Receiver 2_3 ................................ ................................ 141 B 7 MLS Directional Front: Receiver 3_1 ................................ ................................ 141 B 8 MLS Directional Front: Receiver 3_2 ................................ ................................ 141 B 9 MLS Directional Front: Receiver 3_3 ................................ ................................ 142 B 10 MLS Omnidirectional Front: Receiver 1_1 ................................ ........................ 142 B 11 MLS Omnidirectional Front: Receiver 1_2 ................................ ........................ 142 B 12 MLS Omnidirectional Front: Receiver 1_3 ................................ ........................ 142 B 13 MLS Omnidirectional Front: Receiver 1_4 ................................ ........................ 143 B 14 MLS Omnidirectional Front: Receiver 1_5 ................................ ........................ 143 B 15 MLS Omnidirectional Front: Receiver 2_1 ................................ ........................ 143

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14 B 16 MLS Omnidirectional Front: Receiver 2_2 ................................ ........................ 143 B 17 Omnidirectional Front: Receiver 2_3 ................................ ................................ 144 B 18 MLS Omnidirectional Front: Receiver 2_4 ................................ ........................ 144 B 19 MLS Omnidirectional Front: Receiver 2_5 ................................ ........................ 144 B 20 MLS Omnidirectional Front: Receiver 3_1 ................................ ........................ 144 B 21 MLS Omnidirectional Front: Receiver 3_2 ................................ ........................ 145 B 22 MLS Omnidirectional Front: Receiver 3_3 ................................ ........................ 145 B 23 MLS Omnidirectional Front: Receiver 3_4 ................................ ........................ 145 B 24 MLS Omnidirectional Front: Receiver 3_5 ................................ ........................ 145

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15 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science in Architectural Studies A COMPARISON OF SOURCE TYPES AND THEIR IMPACTS ON ACOU STICAL METRICS By Keely Siebein August 2012 Chair: Martin Gold Cochair: Gary Siebein Major: Architecture The purpose of this study is to compare acoustical measurements made with different source types in a relatively reverberant room to determine if ISO 3382 monaural acoustic parameters such as Reverberation Time (RT), Early Decay Time (EDT), and Clarity Index (C 80 ), yield different results for natural acoustic versus calibrated source stimuli. The source stimuli used in the study included Maximum Le ngth Sequences (MLS), a running train of speech, a running piece of music and a balloon pop. The scientifically calibrated method is then compared to acoustical measurements obtained from natural acoustic sources, which include anechoic recordings of voic e and music played through a directional loud speaker in the front of the room to simulate activities that would normally take place in the room, such as a person speaking and music being played during a worship service. This analysis is performed to determ ine if there are differences in acoustic room parameters using natural acoustic sources. This study essentially compares the effects of different source stimuli on measured acoustic parameters.

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16 It was found that different source signals and receiver locat ions significantly affect the acoustic metrics derived from the acoustical measurements due to variations in frequency, level and directionality.

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17 CHAPTER 1 INTRODUCTION The goal of this study is to determine if different sound sources have an effect on the acoustical metrics derived from acoustical measurements taken in a room. Acoustical metrics are typically given as a single number ave rage value for the entire room. These measurements are usually performed in accordance with ISO 3382, with an omnidirectional loudspeaker playing a Maximum Length Sequence (MLS) or sine sweep signal from a loudspeaker from which impulse responses are deri ved. Are the acoustical metrics derived from these measurements applicable to all the sounds that are normally heard in the room? T his question is pertinent because if one can understand how rooms affect the specific sounds produced within them, one can more accurately design for improved acoustics in these spaces. One cannot de sign a room solely based on numerical criteria. The numerical criteria do not address the room as a whole; they serve as an attempt to quanti fy the complex interactions of sound and environment. Recent research in soundscape theory emphasizes the importance of understanding how rooms are used by the people who inhabit them, and what kinds of sounds are made and listened to in these spaces. This soundscape method is at the heart of this study, in that by identifying sounds that might typically take place in the Baughman Center and deriving acoustical metrics from them, a deeper understanding of how the space affects these different sound sources is possible. Rese arch has been conducted in the past ten years based on findings that there are multiple acoustic metric values in one space. For example, Taeko Akama et al. conducted research that entailed a matrix of between 511 and 1427 receiver position

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18 some in almos t every seat of a concert hall to determine how the different seat positions affect the acoustic metrics suc h as Reverberation Time, Early Decay Time and Clarity 1 Their study revealed that each seat has different direct and reflected paths from the sour ce to the receiver, and therefore sounds will be heard differently at each seat. Based upon these observations this study was conducted to determine what effect different sources have on acoustical metrics and to relate acoustical metrics taken in general accordance with ISO 3382 to metrics derived from natural sources that might actually take place in the room. 1 T Akama, H Suzuki, and A al Parameters in Concert Halls, Applied Acoustics 71 (2010): 564 577.

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19 CHAPTER 2 LITERATURE REVIEW Architectural Acoustics Acoustics is a relatively young science, with the first scientific experiments performed in the early part of the twentieth century by Wallace Clement Sabine. While W. C. Sabine is most noted for his studies on Reverberation Time; he also recognized basic architectural acoustical concepts, principles of clarity, loudness, distinctne ss, low background noise, and uniform sound distribution. 1 He understood basic architectural concepts as they related to acoustics, such as elevating the sound source in an auditorium above the audience, and raising the rear of the audience seating area t o allow for better comprehension of speech and music. He also understood that putting a wall behind the sound source would provide a surface that sound may strike and propagate back into the audience as early reflections making the sounds louder than they would otherwise be, and that adding a roof to an open auditorium would ensure that sound would not escape the main volume of the audience area. 2 Sabine understood basic acoustic concepts as they relate to the design of auditoria, and that he understood m any of the intricacies that are found in the study of reverberation. explanation of direct and reflected sounds. He refutes what he describes as being the traditional way of thinking; th at direct and reflected sound reinforce each other all the time and therefore increase the loudness of the sound. While this may happen if the sound waves are properly aligned, this is not always the case. Sabine describes the 1 Wallace Clement Sabine, Collected Papers on Acoustics ( New York: Dover Publications 1964), 4. 2 Sabine, Collected Papers 5.

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20 physical characteristics of sound waves and the motion of compression and rarefaction. If one sound path is shorter than the other due to it striking a surface in the rarefaction and therefore result in silenc e. 3 His scientific approach to studying reverberation allowed for a deeper and quantifiable understanding of what was then considered the phenomenon of sound. Sabine defines architectural acoustics as it related to the design of a room by defining two r oom variables: shape and material. 4 His reverberation experiments started with identifying the sound absorption power of various materials. The Reverberation T ime was measured in the room before the addition of any materials, and then in increments of am ounts of materials. The first experiment involved bringing in seat cushions from the nearby Sanders Theater into the Fogg Lecture Hall and measuring how long the reverberation lasted in the room with different amounts of cushions. Other materials were te sted as well including chenille curtains, oriental rugs, Herez (Persian rug), Deminjik, Hindoostanee, cretonne cloth, canvas and hair felt. Sabine even tested the absorption characteristics of a man and woman in a smaller room. 5 Sabine was able to draw several conclusions from the initial experiments that can still be applied today. 6 Testing to come to 3 Sabine, Collected Papers 5 6. 4 Sabine, Collected Papers 10. 5 Sabine, Collected Papers 10 11. 6 Sabine, Collected Papers 17.

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21 this conclusion was performed in Stienert Hall, where R everberation T imes at eight receiver positions were tested. The R everberation Ti mes varied from 2.12 to 2.27 seconds (0.15 seconds difference). 7 While it is true that R everberation T ime may not vary greatly depending upon the receiver location, the paths the sound reflections take from source to receiver changes, and the impulse response will reveal a different pattern of reflections. However, this concept was not discovered for over 80 years after periments. Similarly, Sabine tested various source positions in a room to see if changing the source position had an effect on R everberation T ime. He found 8 An experi ment was performed in the Jefferson Physical Laboratory in which a fixed observer measured the R everberation T ime in six different source positions in the room. This test resulted in R everberation T imes of 3.90 to 4.00 seconds (0.10 seconds difference). 9 Lastly, an experiment was performed in the lecture room of the Fogg Museum to determine if the locations of the absorbent material had an effect on the R everberation T ime. Fifty meters of cretonne cloth were hung in four sections of the room, and the obs erver remained in a fixed position. The resulting R everberation T imes after the addition of the cloth were 4.83 to 4.92 seconds, a difference of 0.09 seconds. 10 the residual sou nd is, under ordinary circumstances, nearly independent of its 7 Sabine, Collected Papers 17 18. 8 Sabine, Collected Papers 18. 9 Sabine, Collected Papers 18. 10 Sabine, Collected Papers 18.

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22 11 This is true, however, Sabine also noted that placement of the absorbent the way for architectural acoustics to move out of what was considered a black art into the re alm of science by performing replicable scientific experiments in many rooms with a variety of conditions. It was said that Sabine had a strong desire to ensure that his experiments were able to withstand scrutiny. In the Introduction to the Dover Editio n of Collected Papers on Acoustics uncommon reluctance to publish the results of an experiment until he was sure it was 12 Fine Structure of Rev erberation Reverberation Time was considered the only acoustical parameter necessary for d escribing room conditions for approximately 50 years From the Reverberation Time criteria, many other criteria were developed that break apart the reflection structure associated with the sound decay to better understand how the room affects the sounds within it. Criteria were developed that were based on sound dec ay, a different slope of the level versus time curve is shown depending on whether the excitation in the room is steady state or impulsive. 13 Atal et al. as summarized by Cremer recommended the Initial Reverberation Time as a room acoustics criterion instea d of the traditional Reverberation Time. It is denoted 11 Sabine, Collected Papers 18. 12 Sabine, Collected Papers XV. 13 Lothar Cremer Principles and Applications of Room Acoust ics. (London: Applied Science, 1982), 414.

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23 as T I It is defined in terms of the time required for a 60 dB decay, but comes from a straight line fitted to the slope of the 1 st 160ms or the first 15dB of decay. This is related to Times in a hall. It was found that there are extreme fluctuations that follow the cessation of steady state excitation. Th ese fluctuations do not allow for accurate assessment of the early part of the reverberation decay using classical methods. 14 Kurer and Kurze showed that different source receiver locations produce different initial slopes given by T I. in which he tested the Reverberat ion Times in various source and receiver locations throughout the room and found small variations of up to .15 seconds using the full 60 dB of decay They also discovered that T I may exceed T when evaluated from 5 and 35 dB, resulting in sagging and bal looned curves of level vs. time. Kurer and Kurze also found that using the region between 0 and 20dB to define the initial slope was helpful. It was denoted as T A or Anfangsnachhallzeit 15 V. Jordan restricted the decay range to just 0 to 10dB, which he referred to as the early decay time or EDT. 16 E Cremer also comments t hat measuring with the backwards integration of an impulse allows the shortening of the range from 0 to 10dB, especially if the slope is evaluated with a computer and not by hand. 17 14 Room Acoustics 414 415. 15 Room Acoustics 415. 16 Room Acoustics 415. 17 Room Acoustics 415.

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24 Impulse Response Overview equations, Manfred Schroeder developed an alternative method of measuring Reverberation T ime in a room and published his first paper on this new method in 1964. He called this integrated impulse response method 18 Schroeder recognized that with the traditional methods of obtaining R everberation T imes, the randomness of the source signal created diffic ulties. Differences in the decay curves are found with a bandpass filtered 19 These differences are cause d by the initial amplitudes and phase angles of the normal modes being different as the source signal shuts off. 20 Averaging the measurements together usually compensates for these differences. Schroeder states that averaging the measurements fails for tw o reasons: first, because it does not reveal the true nature of the decay curve, and second, because it cannot detect multiple decay rates and especially high initial decays. Schroeder asserts that the initial part of the decay curve contains valuable inf ormation, as recent research had indicated that may be as important as the later decay when analyzing the reverberance of a space. Schroeder states that the new method that he has developed will have the same effect as averaging an infinite number 18 M. R. Schroede Mea suring Reverberation Time The Journal of the Acoustical Society of America 37 ( 1965): 411. 19 Schroeder, New Method 409. 20 Schroeder, New Method 409.

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25 of band pass filtered noise decay curves. 21 Indeed, the impulse response method that was ahead of its time and has only recently been acknowledged as a scientifically calibrated method for obtaining the R everberation T ime in International and American standards. The standards will be discussed in a later portion of the text. An impulse response is composed of the direct sound and the discrete, separate reflections from various room surfaces that follow it. Several methods were identified to attempt to represen t the best method of revealing the impulse response. There are several methods to provide the impulsive sound that is measured by the impulse response. A pistol such as one used for starting races was often used when testing the R everberation T ime in a r oom. W. Reichardt has shown that the spectral distribution of 22 It is for this reason a pistol is considered appropriate for evaluating speech qualities in a room. Another method is a loudspeaker that radiates a pre filtered signal, such as a Gauss tone impulse. Gauss tone impulses, which are considered especially distortionless, are short pure tone impulses wh ose time enveloped is shaped like the bell shaped Gaussian distribution. However, these curves may represent responses that are representative of our ears, yet experience has shown they are not well suited for detailed analysis with echograms. Lehmann de monstrated in an experiment that using Gauss tones can lead to very different impulse responses when changing the source and receiver only several centimeters. Our ears do not detect these kinds of minute differences in distances in 21 Schroeder, New Method 409. 22 Room Acoustics 418.

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26 large halls; therefore this method is not best suited for impulse response measurements. 23 Schodder performed experiments in which source and receiver locations were varied in the Royal Festival Hall, and impulse responses recorded. Upon review and comparison of the impulse res ponses, it was clearly evident that source and receiver positions had a great effect on the impulse response. Each source and receiver position had extremely varied impulse responses from one another. 24 Cremer suggests that based upon this evidence, it is not fitting to refer to the acoustical attributes of a hall without at least mentioning where the source and receiver were located for the measurement. 25 Comparison of the Early and Late Portions of the Impulse Response It has been established that the d irect sound, first reflection and subsequent the useful sound with the total sound in ratio form. 26 The equation is: squared (p 2 ) over the integral of sound pressure squared (p 2 ) of the total sound from 0 23 Room Acoustics 419 419. 24 Room Acoustics 420. 25 Room Acoustics 420 421. 26 Room Acoustics 430.

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27 27 Beranek and to early sound ra equation is: The new equation takes the integral of the sound pressure squared (p 2 divided by the integral of sound pressure squared (p 2 ) from 0 to 50ms. It was found that 10 log of this ratio is the reverberation index of Hallmass. The equation is: ) dB These metrics only consider sound after 50ms to be reverberant sound. However it was found that the limit of perceptibility is not a constant time, but rather depends on the character of the signal. 28 Based on this idea, Reichardt proposed a value of 80ms as the limit of perceptibility of eference to music. 29 His equation is: This equation takes the ratio of the integral of sound pressure square from 0 to 80ms equations are problematic in that a very slight shift in arrival time of a strong reflection 27 Room Acoustics 430. 28 L. L. Beranek and T. J. nces in the Design and Testing of Concert Acustica 15 (1965): 307. 29 Room Acoustics 431 432.

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28 can significantly change the value of the criterion. 30 Lochner and Burger are able to ed a weighting factor ( ) that lessens the change from useful to non useful sound that depends on the delay time and the relative level of the reflection. 31 This new equation reads: The useful energy is the integral from 0 to 95ms of sound pressure squared multiplied by the weighting factor ( ). The detrimental energy is the inte g sound pressure squared. Jordan goes on to propose another s imilar criterion called the response corresponds to the onset of steady state excitation. It is defined as the moment in the impulse response where the early and lat e energy are equal and as such is also the time required to reach a level 3 dB below the asymptotic final level. 32 The equation is This equation shows the integral from 0 to the rise time ( ) of sound pressure squared is eq ual to the integral from the 30 Room Acoustics 431. 31 J. P. A. Lochner and J. F. Burger, Acustic a 8 (1958): 1. 32 V. L. up Process of Sound Pulses in a Room and its Relation to Conce rt Hall Proceedings of the 3rd ICA, Stuttgart, 1959, Vol. II ( Amsterdam : Elsevier, 1961 ), 922.

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29 early to late energy in an impulse response allows for several methods of analysis that are useful when determining acoustical characteristics of a room. 33 Acoustical Criteria This study focuses on several acoustical criteria based on room geometry and materiality including R everbera tion Time Early Decay Time, Clarity/Intelligibility and a diffuse sound field. These concepts are expanded upon below. Reverbera tion Rev erberation is defined as the sound that persists in a room after a source is suddenly stopped 34 It is measured by the Reverberation Time, which is the amount of time it takes a sound to decay 60dB from the level of the stimulus such as the stop chord. Th e Sabine Reverberation Time equation is V is the room volume in ft 3 S is the surface area in ft 2 coefficient in the room. This requires general information about the room, including the volume and absorption in the room. The reverbera tion is contr olled by the ceiling height, the volume of the space and the materials in the space. A desired Reverberation Time can provide a general idea as to how tall the ceiling should be, but does not describe where absorption needs to be placed in the room. In performance spaces, it is necessary to have an adequate ceiling height and volume so that there is enough reverbera tion in the space. The audien ce is generally the largest sound absorbent area 33 Room Acoustics 433. 34 L L Beranek, Concert and Opera Halls: How They Sound (Woodbury, NY: Published for the Acoustical Societ y of America through the American Institute of Physics, 1996), 23.

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30 in a room that is designed for music. Reverberation Time is one of the most commonly used criteria for assessing the acoustical performance of a room. Early Decay Time Early Decay Time measures the first 1 0, 15 or 20 seconds of sound decay. It is related to clarity, envelopment and spaciousness. Early Decay Time is defined by Jordan as the 35 Jordan goes on to argue that EDT is one of the most relevant acoustical parameters in in comparable data. 36 Jordan examines two main interpretations of EDT measures. The first is that the EDT is used when calculating the Inversion Index, which is the ratio of the EDT in the audience divided by the EDT value of the stage area. Jordan also suggests that one can compare the RT and EDT a t individual locations in the audience. He states the RT and EDT should be close, and in halls where the RT is low, having a slightly higher EDT is preferred. 37 present differences in RT and EDT between 0.01 a nd 0.12 seconds. 38 Clarity/Intelligibility Clarity is defined by Egan as the degree to which individual notes are distinct or stand apart. 39 35 V L The Journal of the Acoustical Society of America 47 (1970): 410. 36 37 38 2 39 M. D. Egan Architectural Acoustics (New York: McGraw Hill, 1988) 147.

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31 40 Clarity is measured by the Clarity Index or C 80 This is the the energy in the sound after 80 41 Clarity is the term associated with music, while intelligibility is the te rm associated with the clear perception of speech. Clarity is enhanced by coplanar reflections that reach the listener between 30 and 50 ms for speech signals, and 30 to 80 ms for music. 42 If these reflectio ns occur within the first 50 to 80 ms, they rein force the loudness of the sound as well. The shaping of the ceiling should provide these coplanar reflections so that the audience receives multiple reflections. There is also the concept of horizontal clarity, which is described as the ability to hear s uccessive notes in a piece of music. 43 In a main theater space, the ceiling over the stage and the audience should be shaped so that these reflections will occur. musical 44 This is quantitatively measured by the ratio of the early sound in the first 80ms to the reverberant sound from 80ms on. In this equation, 10 log is multiplied by the ratio of the integral of the first 80ms of 40 Beranek, Concert and Opera Halls 41. 41 Beranek, Concert and Opera Halls 570. 42 P. S. Veneklasen Auditorium Acoustics ed. by Robin MacKenzie. (New York: John Wiley and Sons, 1974), 21 43. 43 Beranek, Concert and Opera Halls 30. 44 Beranek, Concert and Opera Halls 23.

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32 a concert hall, the 80ms time period is considered the optimal time period for early reflections to arrive to increase t he clarity in the room. 45 One coplanar ceiling reflection in the first 40ms is desirable to create this effect. 46 Diffuse Sound Field A diffuse sound field occurs when sounds propagate equally over the space. It is measured by the Inter Aural Correlation Coefficient (IACC) difference in sounds arriving at the two ears of a listener facing the performing entity in 47 It relates to the amount of diffusion present in a space. The IACC metric ranges from 0 to 1, and lower IACC values are desirable. To achieve low IACC values, it is necessary to provide diffusion in the low, middle and high frequencies by providing diffusion of different widths. Beranek reported measured IACC values of 31 concert halls and found that 74% h ad IACC values of less than 0.40 in both the 500 and 1,000 Hertz octave bands 48 While the IACC metric is not examined in this study, the concept of a diffuse sound field is important as it is the basis for acoustical measurements. The standards dictate t he use of an omnidirectional loudspeaker so that it may create a diffuse sound field in the room. However, it is nearly impossible to have a truly diffuse sound field in any room, as the room is almost always never completely diffuse and there are very fe w if any truly omnidirectional sound sources that would excite the room in this manner. 45 W. Acustica 32 (1975): 126. 46 43. 47 Beranek, Concert and Opera Halls 569. 48 Beranek Concert and Opera Halls 535, 593 617.

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33 While understanding the technical definitions of acoustical criteria are necessary to provi de a background for the study, a philosophical framework is needed to put the ideas into context and to develop a measurement method that is founded on solid scientific and perceptual principals. Soundscape Theory referenced in the field of acoustics. 49 While leaving the definition simple, it allows interpretation and does not place unnecessary restrictions on attempting to specifically define the term. He challenges humans to conside soundscape of the world an indeterminate composition over which we have no control, 50 Humans are responsible for a grea t number of sounds in the soundscape at any given period of time, from planes and automobiles, to the hum of a laptop in a coffee shop and the clicking of fingers on the keyboards to a ringtone heard as a cell phone rings, we introduce a multitude of sound s into our environment. Similarly, humans are not only responsible for making sounds, but they are responsible for creating spaces where sounds are altered. From the acoustic designer and architect who mold the buildings floors, walls and ceilings, to the interior designer who de signs the interior of the space to 49 R. M. Schafer The Soundscape: Ou r Sonic Environment and the Tuning of the World (Rochester, VT: Destiny Books, 1994), 7. 50 Schafer, The Soundscape 5.

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34 the end user, who changes the space even more once occupied, humans are responsible for creating the space in which sounds take place. 51 interior designers, landscape architects and urban planners to integrate the conscious design of the sonic attributes of the environments they plan, design and construct as a part of their typical 52 Sounds cape theory can be used to assist in identifying the types of sounds that typically take place in a building so that the acoustical attributes can be designed with them in mind. By identifying the constituents that make up the soundscape in a worship spac e, typical source types and locations can be identified, as well as itineraries and acoustic calendars can be defined to provide a more holistic understanding of the space. With knowledge of the types of sounds that typically take place in the building, h ow do typical scientifically calibrated acoustic measurements compare to the sound sources that excite the room? Are the metrics derived from the scientifically calibrated sound sources comparable to metrics derived from natural acoustic sources that woul d typically be heard in the room? Schafer likens the idea of a soundscape to a composition, in which all the parts of the composition are carefully planned and executed: the notes, pauses, tempo, and rhythm. The notes in a song can be likened to the sou nd sources in a soundscape: some occur by themselves, some occur together. There are pauses in the composition, as there are pauses in the soundscape, where sounds cease and there are periods of 51 B. Blesser and L Salter, Spaces Speak, Are You Listening ?: Experiencing Aural Architecture (Cambridge, Mass: MIT Press, 2007), 1 9. 52 G. Designing Soundscape for Sustainable Urban Development Conference, Stockholm, Sweden, September 30 October 1, 2010).

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35 silence. The tempo of the song is likened to the tempo of t he soundscape; some choruses, or notes can be likened to the acoustic calenda r of a soundscape. The acoustic calendar is documented by cataloging the specific sound sources and determining their hourly, daily, weekly, monthly and yearly cycles. A soundscape can tributes of indoor 53 Similarly, Siebein discusses using soundscape analysis, sophisticated measuring and modeling of spaces to allow ace before it is built so as to intelligently design and shape the space. Given this perspective, perhaps using acoustical measurements derived from sound sources that are typical of the room as the basis of the computations for the auralizations could pr ovide even more robust modeling of the space. Using analysis methods that have been developed to understand how sound moves throughout a room, one can see how real sound sources behave in a room as well. The impulse response contains information about h ow the sound interacts with the room. By studying parts of the impulse response, one can understand more about sound and its interactions with the room surfaces. This study examines Reverberation Time, Early Decay Time and Clarity in relation to scientif ically calibrated sound sources and natural acoustic sources, such as anechoic speech and music. 53

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36 Worship Space Acoustics Youngmin Kwon performed a study in which acoustical measurements wer e conducted using a single omni directional loudspeaker located in the middle of the stage as the source and compared it to measurements conducted using an array of multiple directional loudspeakers set up on the stage to simulate an orchestra. The directional loudspeakers were carefully placed in locations where ins truments are typically placed, and each speaker was to represent an individual instrument section of a full orchestra. The loudspeaker was placed so that its directionality matched the directionality of the instrument it was to simulate. It was found tha t there were not significant differences in RT and EDT, however, there were differences in C 80 values depending upon receiver location. 54 Soeta et al. compared acoustical measurements made in 4 churches ranging in room volume from 1,000 and 12,600 m 3 So urces were arranged using locatio ns proposed by Martelotta et al as well as locations described in the Catholic liturgy. A directional loudspeaker at 1.5m above the finish floor was used to simulate sound propagating into the room from a person speaking in the room at 2 source locations. The directionality of the loudspeaker was measured and compared to the directionality of a human mouth. Soeta et al found that even though the directivity pattern of the directional loudspeaker did not directly corres pond to the human mouth, it provided a better approximation than an omnidirectional speaker would of the directivity pattern of a human mouth. It was observed that there was little variation between source and receiver position for the RT and EDT from 125 to 1,000 Hertz. It was found that using 54 Y. Balcony Acoustics with Real and Simulated 56.

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37 the sources that faced away from the congregation resulted in lower Strength (G), total amplitude of reflection (A) and C 80 than using the sources facing towards the congregation. 55 Performance Space Acoustics In 19 91, John Bradley performed a study comparing three concert halls: the Amsterdam Concertgebouw, the Vienna Musikvereinsaal, and Boston Symphony Hall. Acoustic metrics were derived from measurements taken in multiple source and receiver locations. It was f ound that th e Reverberation T imes did not v ary widely throughout the rooms ( + 0.1 s in the middle and high frequencies). 56 Reverberation T imes and Early Decay Times had a tendency to have similar values despite being derived from measurements from three di fferent source locations ( + 0.1 s in the middle frequencies). 57 When different receiver positions were used, the values for the R everberation T imes remained mostly constant, however EDT values varied in each EDT values increase with increasing source receiver distance, C 80 58 He also found that the EDT values and RT values varied from each other by approximately + 0.1 seconds 59 55 Y. Sound Source Location The Journal of the Acoustical Society of America 131 (2012): 1218 1219. 56 J. S. The Journal of the Acoustical Socie ty of America 89 (1991): 1811 57 58 59

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38 Balloon Pop Study Recent studies were performed by Ptynen et al that examined the directivity pattern and power spectrum of balloons. Balloons of different color, size and inflation were tested in an anechoic chamber with a spherical microphone array. It was determined that larger balloons had more energy and balloons that were more inflated had more energy content in the high frequencies. It was also determined that while balloon directivity patterns were mostly stable, they do not satisfy stipulations in ISO 3382 regarding the source hav ing omnidirectional propagation. 60 Therefore, if Balloon Pop s are to be a sound source in acoustical measurements, it is best to use large balloons that have been inflated as much as possible. Omnidirectional Speaker Study A study was completed by Ricard o San Martin and Miguel Arana on differences in acoustic metrics derived from performing acoustical measurements with four different omnidirectional speakers in five halls using simulations using Odeon room acoustics software. A grid of over 3,000 receive r positions were measured as the source was rotated 5 o It was found that below 1,000 Hertz, differences in acoustic metrics were not prominent. However, in the 1,000 and 2,000 Hertz octave bands, uncertainties based on the subjectively perceivable chang e was from 15% to 40% respectively. Octave bands higher than 2,000 Hertz were found to have deviations greater than half the Just Noticeable Difference of the acoustic metric in over 80% of the receiver positions. 61 60 J. Patynen, B F. G. Katz, and T The Journal of the Acoustical Society of America 129 ( 2011): 27 61 R. S. Martin and M Acoustic The Journal of the Acoustical Society of America 123 (2008): 137.

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39 Therefore, even omnidirectional loudspe akers do not have entirely reproducible signals, despite the intent of the standards that prescribe the use of them. Directivity of Sources The way in which sound radiates from the source to the receiver in each octave band is referred to as the direc tivity of the source. The directivity of a source is often plotted on a polar coordinate graph to show the directional characteristics of the source. The directionality of a human voice is plotted in Figure 2 1 The high frequencies which are associate d with consonant sounds have much more energy to the front of the speaker, as opposed to the rear, which can be reduced up to 20dB from the front. 62 Figure 2 1 Polar plot of the directionality of human voice in 5 00 and 4,000 Hertz octave bands C redit : M. D. Egan Architectural Acoustics p. 83 The directionality of a trumpet is shown in Figure 2 2 The lower frequencies tend to be more omnidirectional, while the high frequencies tend to propagate directly from 62 Egan, Architectural Acoustics 83.

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40 the horn of the instrument. 63 Figure 2 2 Polar plot of the directionality of trumpet in 220, 480, 920, 1840 and 4,000 H ertz octave bands C redit H. F. Olson Music, Physics and Engineering p. 235 Figure 2 3 shows the directivity patterns of medium and large balloons. The balloons tend to have more omnidirectional directivity in the 1,000 and 2,000 Hertz octave bands than in the 125, 250, 500, and 4,000 Hertz octave bands Figure 2 3 Directivity patterns of medium and large balloons C redit : P tynen et al., Investigations on the bal loon as an impulse source p. 30 The directivity pattern of the JBL EON 15 G2 that was used in these studies is shown in Figure 2 4 The low and middle frequencies have directivity patterns that propagate omnidirectionally. However, the high frequencies including 8,000 Hertz and above tend to propagate towards the front of the speaker. 63 H.F. Olson, Music, Physics and Engineering (New York: Dover Publications, Inc.,1967), 235.

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41 Figure 2 4 Polar plot of JBL EON15 G2 i n the 500, 1,000 and 4,000 Hertz frequencies showing 3. 6 and 9dB radii Figure 2 5 shows the approximate directivity pattern of the Norsonic 223 dodecahedral loudspeaker. Exact polar plots of the Norsonic 223 dodecahedral loudspeaker were not available as the loudspeaker is an older model. However, the manufacturer provided the polar plot in Figure 2 5 as an approximation of the Norsonic 223, as it is a polar plot of a similar updated dodecahedral loudspeaker. The low and middle frequencies of 100, 3 15 and 1,000 Hertz tend to radiate omnidirectionally. The higher frequencies of 3,150 Hertz and above radiate directionally from each of the twelve speakers, which are shown with the brown undulations in F igure 2 5 Reverberation Time: Traditiona l Equations and Acoustical Standards Traditional Equations Several methods for obtaining the R everberation T ime are discussed below, as they are used in this study. The Sabine Equation for R everberation T ime is generally used for rooms that are not highl y absorbent and when there is a mostly diffuse sound field. 64 The Equation is as follows: 64 Sabine, Collected Papers 39.

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42 T is the Reverberation T ime in seconds. V is the room volume in ft 3 surface area of room absorption in sabins. Figure 2 5 Polar plot of the Norsonic 276 loudspeaker, which was provided by the m anufacturer as a comparable polar plot to the Norsonic 223 loudspeaker Credit: Nor276 Dodecahedron Loudspeaker [cited 12 July 2012]. Available from http://www.norsonic.com/index.php?sideID=6962&ledd1=6981 The Norris Eyring equation is another equation used to estimate the R everberation T ime in a room. It is generally used for rooms that are more absorbent. Th e Norris Eyring equation is as follows: T is the R everberation T ime in seconds. V is the room volume in ft 3 S is the total surface area in ft 2 is the mean sound absorption coefficient. 65 65 Beranek, Concert and Opera Halls 620.

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43 Acoustical Standards ISO 3382 R everberation T i 3382 standard details measurement procedure s for the measurement of room acoustic par ameters. It contains descriptions of measurement techniques using both the interrupted noise and the impulse response methods to derive acoustical parameters. The ISO 3382 standard define s Reverberation T ime as the time required for the level to decrease by 60 dB, at a rate of decay given by the linear least squares regression of the measured decay curve from a level 5dB below the initial level 66 omni direct than 2 meters, so they are at least half a wavelength apart. 67 For low and normal coverage measurements, a minimum of 2 source positions should be used and located in the typical sour ce positions. For example, in a room such as a worship space or classroom, where a speaker is typically located in the front of the room facing the audience, the loudspeaker should be placed in this same position. Three to four microphone positions are r ecommended for the receivers. 68 It is noted that the measurements should include octave bands from 63 to 4,000 Hertz in concert halls and 66 Measurement of the reverberation time of rooms with ref erence to other 67 ISO 3382, 4. 68 ISO 3382, 5.

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44 rooms for speech. 69 For impulse response measurements, a linear least squares fit line is used to determine the slope of the reverberation decay. The impulse response method is used in this study as the scientifically calibrated acoustical measurement system. As such, the ISO standard is referenced and provides the basis for which the scientifically calibrated measureme nts are taken, as it is the only standard the specifically deals with the measurement of rooms using the impulse response method. ASTM E 2235 The ASTM E 2235 Standard is the only American standard the deals with R everberation T ime. However, this standar d must be used in conjunction with acoustical testing of partitions. Unlike the ISO 3382 standard, i t does not dictate measurement procedure to determine R everberation T ime on its own. The ASTM E2235 t method shall not be used when room sound absorption or decay rate is to be used directly to satisfy some criterion, for example in a room that must not be overly reverberant so speech will be 70 the room absorption will usually be too high and additional measurements are The ASTM standard requires an omnidirectional speaker, but makes an allowance to cover different frequency ranges 71 This typically 69 ISO 3382, 6. 70 Metho 71 ASTM E 2235, 1252.

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45 means a 2 or 3 way loudspeaker, which is inherently directional. This however, is not explicit in stating what the intent of the e xpression is. It may be allowing for directional loud speakers, as long as they are placed in the corners of the room The standard calls for at least one source position, but does not specify or recommend the location it should be placed. 72 At least three receiver locations are called for. 73 When determining the decay rate, the standard specifies that the first point 74 Section 16.1 specifies that all points of analysis must be 10 dB above the background noise level. Despite that this standard is not to be used as the sole method for determining the R everberation T ime in a room, it must be referenced for this study as it is the only American standard that addresses this measurement protocol. Just Noticeable Differences in Acoustical Metrics perceivable change detec ted by 50% of the subjects. In statistical terms, this value is 75 ime and C 80 values for each sound source tested are discussed below. Reverberation Time In terms of Reverbe ration T ime, Cremer cites an article written by H.P. Seraphim in 1958 in which approximately 500 test subjects were given listening tests to determine 72 ASTM E 2235, 1252. 73 ASTM E 2235, 1253. 74 ASTM E 2235, 1253. 75 F. Martellotta, Spaces. The Journal of the Acoustical Society of America 128 ( 2010): 659.

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46 Just Noticeable Differences in Reverberation T ime. The relative difference limen for Reverberation Time referring to the change in Reverberation Time divided by the Reverberation Time. It 76 Cremer continues that some subjects were musically trained, and that 4% should be used as the just noticeable difference term. 77 Several references to the subjective difference limen were also found, however they did not include the origi nal source information where the number originated. Kleiner, Klepper and Torres mention in Worship Space Acoustics that changes of less than 5% in R everberation T ime can be noticed. 78 Ingolf Bork wrote a series of papers on acoustical measurement simulat ions in which he uses 5 ms as the subjective difference limen for R everberation T ime 79 The original source from which he obtained the 5ms for the subjective difference limen is not indic ated in the text of the article E arly D ecay T ime Martellotta performed a study on the Just Noticeable Difference in Center Time and Clarity in reverberant spaces in 2010. Martellotta includes a table that has Just Noticeable Difference values of 0.05% for Early Decay Time in his study 80 In a study 76 Room Acoustics 505. 77 Room Acoustics 505. 78 M. Kleiner, D. L. Klepper, and R R. Torres, Worship Space Acoustics (Ft. Lauderdale: J. Ross Pub lishing, 2010), 91. 79 I. Bork, The Journal of the Acoustical Society of America 105 ( 1999): 753 763. 80

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47 performed by Sk levik that establishes that Reverberation Time, volume and source receiver distance can predict sound level, reverberance, clarity, apparent source width study, but does not list an original source as to how this value was determined 81 Clarity ( C 80 ) John Bradley et al performed a study in which the JND for the clarity index for speech, C 50 was tested. Subjects listened to simulated sound fields and made determinatio ns between which were the same and which were different. 82 This experiment determined that there is a 1.1 dB JND for C 50 and that the equation used to generate the relationship can also be applie d to C 80 resulting in a JND of 0.9 dB for C 80 83 Ahearn et al performed a study in the past several years in which 51 musically trained subjects were given listening tests to determine JNDs for music motifs in an anechoic chamber that was digitally configured to have 1.6 and 2.1 second R everberation T imes. Resul ts from all participants yielded little information, however, the JND. 84 81 M. Sklevik, Proceedings of the 20th International Conference on Acoustics Sydney, Australia (August 23 27, 2010): 1 2. 82 J. S. Applied Acoustics 58 (1999): 100. 83 105. 84 M. J. The Journal of the Acoustical Society of America 126 ( 2009): 2288.

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48 Martellotta performed an experiment in which acoustic measurements for 3 large spaces with differen t long R everberation T imes were performed to determine if the R everberation T ime affected the JND for clarity metrics. 85 The R everberation T imes for the spaces were 2.1, 4.1 and 6.0 seconds. 86 It was found that in these larger spaces with longer R everberat ion T imes, the JND for C 80 was 1.48 + 0.13 dB. 87 This value will be used as it relates to spaces with longer R everberation T imes than the other literature. The technical concepts background, relevant studies, standards and soundscape theory serve as the theoretical and philosophical framework that is at the heart of the study. Scientifically calibrated acoustical measurements are not representative of the real so unds that happen in a room. By analyzing a space with th e soundscape method and understanding the acoustic events that actually take place in a space, one can begin to appreciate how those sounds are affected by the room. By deriving acoustic metrics from natural acoustic sources one can begin to have a deeper understanding of how a space affects sounds that take place within it 85 86 87

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49 CHAPTER 3 ACOUSTIC SOURCE COMPARISON STUDIES General Information The Baughman Center is a non denominational chapel located on the University of Florida campus. Constructed in 2000, it is made of low E energy efficient glass, and the exterior is Florida cypress. The interior of the chapel is painted structural steel, southern yello w pine tongue in groove roof planking and gypsum board. It s area measures approximately 1500 feet 2 accommodate up to 96 people seated. 1 Floor Plan The floor plan in the Baughman Center is co nsidered a rectangular shape. The the maximum distance an untrained speaker can n aturally project into a space with out the need for amplification. 2 Reverberation Average R everberation T imes in worship spaces vary from 1 second to 3 seconds. For a room with a volume similar to the Baughman Center, the desired R everberation T ime is .07 seconds for unassisted speech to 1.3 seconds in the 500 Hertz octave band for chamber music and choral music for a space that is approximately 1,152m 3 The measured R everberation T ime in the Baughman Center is approximately 2.6 seconds in 1 Baughman Center [Web site] (2010); available from http://performingarts.ufl.edu/venues/baughman center/ ; Internet; accessed 10 August 2010. 2 M. Kleiner, D. L. Klepper, and R R. Torres, Worship Space Acoustics (Ft. Lauderdale: J. Ross Publishing, 2010), 83.

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50 the 500 Hertz o ctave band using the Maximum Length Sequence (MLS) measurement procedure At the highest peak, the ceiling height is 44 feet the lowest point is 20 feet 6 inches and on average 32 feet 4inches Materials Rooms for worship are generally made of r eflective surfaces with little sound absorption. The materials in the Baughman Center are hard reflecting surfaces. The roof is constructed of Southern yellow pine tongue in groove planking. The floor is made of travertine marble and the stage area is m ade of maple with inlaid cherry around the exterior. The walls are made of gypsum board and glass windows There are two rows of seating in the Baughman Center, made of maple and cherry, with a light blue fabric upholstery on the seats and backs of the p ews. Pilot Study The pilot study was inspired by a fellow University of Florida student wishing to obtain simple R everberation T ime measurements for the space. When in the space, it was clear that the building design did not affect sound in a desirabl e way. Because of its religious/spiritual context and the fact that the space is used by musical performers from the University of Florida, the building should be able to provide adequate acoustics for speech and music. However, this is not the case. Sp eech and music in the space sound muddy and individual sounds tend to run together. Due to the difficulties for both types of communication, the idea to perform multiple acoustical measurements with varying source signals was developed to determine if aco ustic metrics derived from the various sounds in the room are affected by the signal type Anechoic speech and music signals are compared to s cientifically calibrated signals to determine if the different source signals result in different acoustic metric values.

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51 Method Source signals were generated using WIN MLS software and a laptop computer. A sine sweep, multiple sine sweep and Maximum Length Signals ( MLS ) were generated by a JBL EON 15 G 2 loudspeaker The JBL EON 15 G 2 loudspeaker is a two way speak er that has a frequency response from 39 to 18,000 Hertz. 3 The loudspeaker was placed in the front center of the stage and the left corner of the stage and measured in three receiver locations throughout the audience area. The signal was received by an E arthworks microphone connected to the Digigram VXPocket 2 instrumentation quality sound card input in the computer. The signal is processed on a laptop computer using WinMLS software to derive the impulse response and calculate acoustical measurements suc h as reverberation time. The microphone was mounted on a stand approximately 42" (seated ear height)above the floor. The measurement performed at each receiver location was generated three times. Electronic Signal Results The standard deviation of each source type is shown in Figure 3 1. T he Sine Sweep in the front of the room, the MLS signal in the corner a nd the MLS signal in the front had standard deviation values greater than 0.1 in the 63 Hertz octave band. The remaining octave bands four all sour ce signals had standard deviations as low as 0.1. The measured R everberation T imes for each signal source are shown in Figure 3 2. The values in the 63 Hertz octave band varied from 1.19 to 2.46 seconds across all sources signals. However within each source type, the standard deviation is below 0.1 for all but 3 source signals. 3 Nor276 Dodecahedron Loudspeaker [website] available from http://cn.jblpro.com/catalog/support/getfile.aspx?doctype=3&docid=239 ; Internet; accessed 12 July 2012.

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52 Figure 3 1. Standard Deviation of Reverberation Times from all Scientifically Calibrated Signals To focus the scope of this study on the qualities of the natural acoustic sou rces the middle frequency 500 and 1,000 Hertz octave bands are compared to the additional sources, as these frequencies are the main speech frequencies. As shown in Figure 3 3, the average middle frequency octave bands for the electronic signals vary jus t 0.04 seconds in the 500 Hertz octave band and 0.2 seconds in the 1,000 Hertz octave band at the Receiver 3 position. The values for the 500 Hertz octave band are slightly higher than the 1,000 Hertz octave band for all the electronic signals. The Rever beration Time values in the 500 Hertz octave band are nominally the same based upon the 99% Confidence Interval for the average RT of all the sources. The directional source in the front of the room, and the sine sweep and multiple sine sweep sources with the directional loudspeaker placed in the corner of the room all fell outside the 99% Confidence Interval in the 1,000 Hertz octave band. Due to the nature of how the scientifically calibrated acoustical measurements are performed, and the type of signal s used, the sound emitted in the room for these tests does not accurately reflect the 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 63 125 250 500 1000 2000 4000 8000 Standard Deviation of Reverberation Times in Seconds Octave Band Center Frequency in Hertz Standard Deviation of Scientifically Calibrated Signals Receiver Position 3 Dir corner sine sweep Dir Front Sine Sweep Mult Sine Sweep Dir Corner Mult Sine Sweep Dir Front Dir Front MLS Dir Corner MLS

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53 nature of sounds that are typically produced in the room. T he scientifically calibrated acoustical measurements present a a R everberation T ime that will most likely never happen during the use of the room. Figure 3 2. Comparison of all scientifically calibrated Reverberation Time measurements Sound sources in the room will be directional, such as a human voice and musical instruments, and will not create a diffuse sound field in the room. Therefore, additional measurements were taken that more closely resembled the activities that might normally happen in the room, to evaluate whether the scientifically calibrated test 1 1.5 2 2.5 3 3.5 63 125 250 500 1000 2000 4000 8000 Reverberation Time in Seconds Octave Band Center Frequency in Hertz Reveberation Times for Scientifically Calibrated Sources Receiver Position 3 Dir corner sine sweep Dir corner sine sweep Dir corner sine sweep Dir Front Sine Sweep Dir Front Sine Sweep Dir Front Sine Sweep Mult Sine Sweep Dir Corner Mult Sine Sweep Dir Corner Mult Sine Sweep Dir Corner Mult Sine Sweep Dir Front Mult Sine Sweep Dir Front Mult Sine Sweep Dir Front Dir Front MLS Dir Front MLS Dir Front MLS Dir Corner MLS Dir Corner MLS Dir Corner MLS

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54 signals provide a realistic indicator of the Reverberation T imes associated with realistic sounds that take place in the room. Figure 3 3. Middle frequency Reverberation Times for average scientifically calibrated source signals with 99% Confidence Interval Natural Acoustic Signals In a setting such as the Baughman Center, typical sound sources would include a pastor or speaker talking in the front of the room such as for a wedding or religious ceremony. Music from live sources such as a violin, trumpet, or trombone may also be heard for a musical recital, which sometimes takes place in the chapel. Anechoic s ource signals were chosen that resemble the acoustic events that actually take place in the room. These signals were gen erated and recorded at the three receiver positions so that they could be analyzed to derive acoustic metrics from them 2.1 2.2 2.3 2.4 2.5 2.6 2.7 500 1000 Reverberation Time in Seconds Octave Band Center Frequency in Hertz RT Comparison of Scientifically Calibrated Sources with 99% CI Average Scientifically Calibrated Sources Dir corner sine sweep Dir Front Sine Sweep Mult Sine Sweep Dir Corner Mult Sine Sweep Dir Front Dir Front MLS Dir Corner MLS

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55 Anechoic v oi ce and m usic as measurement sources An anechoic recording of a female voice and trumpet music from the CATT Acoustic pro gram was used so that the exact timing and level could be duplicated at each receiver position. These sources were played into the room using a directional loudspeaker placed at the front center of the room to simulate where a person might actually speak o r where live music might be played. These signals were recorded with the M Audio Microtrack II WAV recorder with an electret microphone at the three measurement locations. The recorded signals were processed using Acoustic Tools software. The stop chord at the end of the was analyzed for this study. Live m usic as a measurement source A middle C note, middle Opera 325 by Johann Strauss Jr. were played on the electronic piano located in the rear of the room. These signals were recorded with the M Audio Microtrack II WAV recorder at the three measurement locations. The recorded signals were processed using Aco ustic Tools software. The stop chord at the end of the piano song phrase was analyzed for this study. The source was located in the opposite end of the room from the source location for the other measurements and is noted in Figure 3 Be cause of this, the receiver location is much closer to the source signal than the other source types. The path from the source to the receiver is much different for the piano sources than from the other measurements

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56 Figure 3 4. Floor plan of Baughman Center showing source and receiver locations Balloon p op as a measurement source Balloons were used as a sound source as well, as they are known for having a strong broad band spectrum burst of sound A balloon was popped in the front center of the room, in the same location that the source playback loudspeaker occupied. The Mictrotrack II WAV recorder was used to record the balloon signal at the three receiver locations in the room. The balloon si gnal was processed using the Win MLS software and Acoustic Tools. The Win MLS software provides a Reverberation Time ( T30 ) without any manual calculation or manipulation. Acoustic Tools requires user input to determine R everberation T imes. Results Figure 3 4 shows the average Reverberation T imes in the middle frequencies for the speech, music and balloon signals. The values for R everberation T imes range from 1.64 to 3.08 in the 500 Hertz octave band and range from 1.96 to 2.91 in the 1,000 Hertz octave b and. The values for the 500 Hertz octave band are greater than the 1,000 Hertz octave band for the Balloon Pop measurements, the Female Talker, and the middle C Chord. The values for the 500 Hertz octave band are less than the 1,000

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57 Hertz octave band for the middle C note, the piano song and the anechoic music p layed through the loudspeaker. Appendix A provides the images from the analysis in Acoustic Tools for the Balloon Pop anechoic Female Talker, Trumpet Song and live piano note, chord and song phr ase. When compared to the electronic sources, the anechoic speech, music, Balloon Pop one of the octave bands shown on Figure 3 6 that includes the electronic s ources and the Balloon Pop analyzed with Win MLS. Figure 3 5 Reverberation T imes for the anechoic speech, music, live music and Balloon Pop sources in receiver position 3 1 1.5 2 2.5 3 3.5 500 1000 Reverberation Time in Seconds Octave Band Center Frequency in Hertz 500 and 1,000 Hertz T30 Values for Natural Acoustic Sources Receiver Position 3 Balloon Pop MLS Balloon POP AT Female Talker Piano Middle C Note Piano Middle C Chord Piano Song Anechoic Music

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58 Figure 3 6 Reverberation T imes in the middle frequencies for all source types Pilot Study Conclusions It was determined that while the R everberation T imes measured with a scientifically calibrated method may provide an idea of how the room responds, ultimately, the R everberation T ime will be affected by the types o f sources. It was found the source type and source location provides variation in the R everberation T imes. The range of Reverberation T imes for the sources tested varied 1.44 seconds in the 500 Hertz octave band and 0.95 seconds in the 1,000 Hertz octave band. It was determined that consistent methods for analyzing the natural acoustic sources were needed. The data varied greatly, and in order to determine if this was due to inconsistencies in the method or if the sources produced that much variation, new methods to analyze the data needed to be developed. Comparing other acoustic metrics from the acoustical measurements take n such as EDT, C 80 STI or D 50 may provide additional insight into the study. 1 1.5 2 2.5 3 3.5 500 1000 Reverberation Time in Seconds Octave Band Center Frequency in Hertz 500 and 1,000 Hertz T30 Values Receiver Position 3 Dir corner sine sweep Dir Front Sine Sweep Mult Sine Sweep Dir Corner Mult Sine Sweep Dir Front Dir Front MLS Dir Corner MLS Balloon Pop MLS Balloon POP AT Female Talker Piano Middle C Note Piano Middle C Chord Piano Song

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59 The impulse response based measurements are internally consistent, as each speaker position and s ource signal generated similar Reverberation T imes in the room. As mentioned previously, when comparing the live music played on the piano, it would be helpful to test other signals at the same locatio n so as to accurately compare the response of the room to that certain path between source and receiver. Source Signal Comparison Method Testing took place on August 24, 2010, September 14, 2010, October, 5, 2010 and on January 23, 2012. It was determined from the pilot study that all three receiver locations should be used. The apparent placement of the speakers in the electronic piano included a speaker that faces out from the rear of the piano and a speaker facing towards the piano pla yer. It would be difficult to set up a speaker to run test signals through that matched this configuration, so it was decided to not concentrate on the data collected from the rear of the room. It was also decided to add the 4,000 Hertz octave band into the final analysis. The natural acoustic signals did not have as much energy in the low frequencies, so analyzing the middle and higher frequencies would allow more data that was collected to be used. Another study was performed that used the Pilot Study as the basis for the measurements, but provided alternative means of analyzing the data. A JBL EON 15 G2 directional source playback loudspeaker was used as the source signal. The source playback loudspeaker was positioned in the front center of the room facing the audience, and in the front left corner of the room facing upward. Three receiver positions were used due to the small room size. Microphones were positioned at approximately 1.5m or seated ear height. Source and Receiver locations are shown in Figure 3 7

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60 Figure 3 7 Floor plan of Baughman Center indicating source types and positions and receiver positions Study 1 : Omnidirectional, Directional and Calculated Comparisons Acoustical measurements were performed using an omnidirectional and directional loudspeaker with an MLS signal. ISO and ASTM dictate that an omnidirectional loudspeaker should be used for acoustical measurements, which will in theory create a diffuse sound field. However, most typical sound sources (human voices, instru ments, etc.) are not omnidirectional and do not excite a room in such a way that they fully excite the reverberant field i n the room Therefore, it was proposed to examine if there are differences in using an omnidirectional and a directional loud speaker on acoustic metrics. These impulse response measurements are compared to each other and to Reverberation Time val u es calculated using the Sabine Equation and the Norris Eyring Equation. The Sabine Equation is a better indicator of the reverberation becau se the chapel is constructed of mostly reflective materials. The Norris Eyring Equation is used for spaces that are sound absorbent. The calculated equations provide whole room averages however e ach scientifically calibrated receiver position is analyze d independently and the results are shown in F igures 3 8 through 3 1 4

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61 Electronic signals Maximum Length S equence (MLS) signals were generated using WIN MLS software and a laptop computer. The MLS signal was generated from a JBL EON 15 G 2 directional lou dspeaker placed in the front center of the stage and the left corner of the stage and measured in three receiver locations throughout the audience area. The JBL EON15 G2 is a two way loudspeaker with a maximum sound power level of 129dB. The MLS signals were also generated with a Norsonic 223 omnidirectional loudspeaker. The omnidirectional loudspeaker is a dodecahedral loudspeaker that consist s speakers with a maximum sound power outlet of 118dB 4 The measurement performed at each receiver l ocation was repeated three to five times. Reverberation t ime The standard deviations for the Reverberation Times derived from acoustical measurements taken with the omnidirectional and directional loudspeaker at each receiver location are shown in Figure s 3 8 through 3 10 In the first receiver location, the directional loudspeaker has lower standard deviation values than the omnidirectional in all octave bands except the 63 Hertz band, which is less than one hundredth of a second in standard deviation from the omnidirectional. The omnidirectional speaker had a standard deviation of 0.23 in the 125 Hertz and 0.11 in the 1,000 Hertz octave band. Both the omnidirectional and directional loudspeakers had standard deviations of less than 0.05 in the 250, 2 ,000, 4,000 and 8,000 Hertz octave bands. 4 Norson ic 213 and 223 Dodecahedron Speaker Specifications [Web site] available from http://www.gracey.com/descriptions/nor_213 d1.htm ; Internet; accessed 12 July 2012.

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62 Figure 3 8 Standard deviation of R everberation T ime for the omnidirectional and directional loudspeaker in the 1 st receiver position Figure 3 9 Standard deviation of R everberation T ime for the omnidirectional and directional loudspeaker in the 2 nd receiver position 0 0.05 0.1 0.15 0.2 0.25 63 125 250 500 1000 2000 4000 8000 Standard Deviation of Reverberatio Time in Seconds Octave Band Center Frequency in Hertz Standard Deviation of Omnidirectional and Directional Louspeakers T30 Measurements: Receiver Position 1 Omnidirectional Receiver 1 Directional Receiver 1 0 0.05 0.1 0.15 0.2 0.25 63 125 250 500 1000 2000 4000 8000 Standard Deviation of Reverberation Time in Seconds Octave Band Center Frequency in Hertz Standard Deviation of Omnidirectional and Directional Louspeakers T30 Measurements: Receiver Position 2 Omnidirectional Receiver 2 Directional Receiver 2

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63 For receiver position 2, the R everberation T imes measured with the directional loudspeaker had lower standard deviation values than the omnidirectional loudspeaker with the exception of the 4,000 Hertz octave band, which is less than 5 thousandths of a second standard deviation from the omnidirectional loudspeaker. The omnidirectional loudspeaker has standard deviation values of less than 0.1 seconds for all but the 63 and 125 Hertz o ctave band at this position. The directional loudspeaker has standard deviations of less than 0.03 in all octave bands. Figure 3 10 Standard deviation of R everberation T ime for the omnidirectional and directional loudspeaker in the 3 rd receiver p osition The standard deviation for the R everberation T ime measurements conducted with the directional speaker was higher than the omnidirectional in the 63, 250 and 2,000 Hertz octave bands for the third receiver location. The standard deviation for the Directional loudspeaker was below .016 for all octave b ands and below 0.09 for all octave bands except the 63 Hertz. The omnidirectional loudspeaker had the highest standard deviation in the 500 Hertz octave band, with a value of 0.18 seconds. 0 0.05 0.1 0.15 0.2 0.25 63 125 250 500 1000 2000 4000 8000 Standard Deviation of Reverberation Time in Seconds Octave Band Center Frequency in Hertz Standard Deviation of Omnidirectional and Directional Louspeakers T30 Measurements: Receiver Position 3 Omnidirectional Receiver 3 Directional Receiver 3

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64 In receiver positions 1 and 2, the Reverberation T ime derived fr om the acoustical measurements made using the directional loudspeaker had lower standard deviations than the omnidirectional speaker in most octave bands. However, in the third receiver position, the highest standard deviation value for the R everberation T ime derived from acoustical measurements made using for the directional speaker at 63 Hz was 0.16. The R everberation T imes derived using the omnidirectional speaker had higher standard deviations in receiver positions 1 and 2. The R everberation T imes d erived from acoustical measurements using the omnidirectional and directional loudspeakers were also compared to calculated R everberation T ime values using the Sabine and Norris Eyring Equations. Figure 3 1 1 shows the averaged R everberation T imes derived from measurements made using the omnidirectional and directional loudspeakers, as well as calculated R everberation T imes derived from the Sabine and Norris Eyring equations. The calculated R everberation T imes are a good approximate for the wh ole room average measured R everberation T imes. Figure 3 1 1 Average measured and calculated Reverberation Times for the Baughman Center 1 1.5 2 2.5 3 3.5 63 125 250 500 1000 2000 4000 8000 Reverberation Time in Seconds Octave Band Center Frequency in Hertz Comparison of Reverberation Time Measurements and Calculations Omni Average MLS Overall Directional Average MLS Overall Sabine Equation Norris Eyring Equation

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65 Clarity ( C 80 ) The R everberation T imes measure d with the omnidirectional and directional loudspeaker in each recei ver position remained relatively consistent. The Clarity Index (C 80 ) or measure of the early to late energy ratio after 80 ms was examined as well. Graphs of the results for the C 80 values are shown in Figures 3 1 2 through 3 14 Three to five measurements were made at each receiver position. These measurements are illustrated in the following graphs using the receiver number followed by the measurement number. For example, the third measurement taken at the 1 st receiver position is noted as Figure 3 1 2 Clarity (C 80 ) values measured at the first receiver position with omnidirectional and directional loudspeakers The C 80 values for the acoustical measurements made using the directional loudspeaker are higher than the values deri ved from acoustical measurements made using the omnidirectional loudspeaker in all octave bands except the 125 Hertz octave -8 -6 -4 -2 0 2 4 6 8 10 63 125 250 500 1000 2000 4000 8000 Clarity (C 80 ) Value in dB Octave Band Center Frequency in Hertz Clarity (C 80 ) Comparison between Omnidirectional and Directional Loudspeakers Receiver 1 Omni MLS Receiver 1_1 Omni MLS Receiver 1_2 Omni MLS Receiver 1_3 Omni MLS Receiver 1_4 Omni MLS Receiver 1_5 Dir MLS Receiver 1_1 Dir MLS Receiver 1_2 Dir MLS Receiver 1_3

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66 bands in the first receiver position. The only octave band that the directional loud speaker had a negative value for was the 125 He rtz octave band. The omnidirectional loud speaker achieved lower C 80 values in all but the 125 Hertz octave bands. C 80 values for the omnidirectional loud speaker ranged from 1.6 to 2.3 dB. T he C 80 values in the 63 Hertz octave band are not noticeably di fferent (0 J ust N oticeable D ifferences or JND ) between the loudspeaker types the C 80 values in the 125 to 2,000 Hertz octave band range between 1 and 2 JND and the C 80 values for the directional loudspeaker in the 8,000 Hertz octave band are 5 JND higher than the omnidirectional loudspeaker Figure 3 1 3 Clarity (C 80 ) values measured at the second receiver position with omnidirectional and directional loudspeakers The acoustical measurements derived from using the omnidirectional loudspeaker achieved slightly higher C 80 values in the 63 and 125 Hertz octave bands than acoustical measurements made with the directional loud speaker in receiver position 2 -8 -6 -4 -2 0 2 4 6 8 10 63 125 250 500 1000 2000 4000 8000 Clarity (C 80 ) Value in dB Octave Band Center Frequency in Hertz Clarity (C 80 ) Comparison between Omnidirectional and Directional Loudspeakers Receiver 2 Omni MLS Rec 2_1 Omni MLS Rec 2_2 Omni MLS Rec 2_3 Omni MLS Rec 2_4 Omni MLS Rec 2_5 Dir MLS Rec 2_1 Dir MLS Rec 2_2 Dir MLS Rec 2_3

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67 However, the acoustical measurements derived from using the directional loud speaker achieved higher C 80 values in the middle and high frequency octave bands. There was not noticeable difference in C80 values for the directional and omnidirectional loudspeaker in the 63 and 250 Hertz octave bands (0 JND) In the 125, 500, 2,000 and 4,000 Hertz octave b ands, the JND ranged from 1 3 between loudspeaker types. The C 80 values for the directional loudspeaker in the 1,000 and 4,000 Hertz octave bands are 4 JND higher than the omnidirectional values. Figure 3 1 4 Clarity (C 80 ) values measured at the th ird receiver position with omnidirectional and directional loudspeakers The acoustical measurements derived from using the omnidirectional loud speaker achieved negative C 80 values in all the octave bands in the third receiver position. The acoustical meas urements derived from using directional loud speaker had higher C 80 values than the omnidirectional in all octave bands. The values for C 80 derived from the directional loudspeaker were not noticeably different than values for C 80 derived from the omnidirectional loudspeaker (0 JND) The directional loudshpeaker had C 80 values -8 -6 -4 -2 0 2 4 6 8 10 63 125 250 500 1000 2000 4000 8000 Clarity (C 80 ) Value in dB Octave Band Center Frequency in Hertz Clarity (C 80 ) Comparison between Omnidirectional and Directional Loudspeakers Receiver 3 Omni MLS Rec 3_1 Omni MLS Rec 3_2 Omni MLS Rec 3_3 Omni MLS Rec 3_4 Omni MLS Rec 3_5 Dir MLS Rec 3_1 Dir MLS Rec 3_2

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68 that were 1 3 JND higher than the omnidirectional loudspeaker in the 125 through 4,000 Hertz octave bands. The C 80 values for the directional loudspeaker i n the 8,000 Hertz octave band are 4 JND higher th a n the omnidirectional loudspeaker. Study 2 : Anechoic Music and Speech and Balloon Pop Stimuli Comparison This analysis looks at a modified version of the pilot study and compares the acoustical metric s derived from using anechoic speech and music and Balloon Pop stimuli by 4 methods. Anechoic music and speech were played through the JBL EON G12 directional loudspeaker and recorded with a binaural M Audio WAV recorder to simulate how the room affect s t hese signals with a reproducible means. The source location was at the front center of the room. The receiver locations were placed in the front, middle and rear of the room, in the same receiver locations used in the previous studies. Please re fer to F igure 3 4 page 5 8 for the source and receiver locations. To analyze how the room would be affected by source located in the front center of the space, only the loudspeaker placed in the front of the room wa s analyzed. There were 4 binaural methods used to determine the acoustic metrics from the anechoic sound sources. Each method Traditional, Expanded, Perceptual and Perceptual WinMLS, is described in detail below. Traditional m ethod T es the decay curve of the source signal and the ISO 3382 protocol th at dictates that the linear least squares regression start at a point 5 dB below the initial sound level 5 Acoustic Tools software was used dule of the software program, the direct sound cursor was placed at the top of the decay curve when the sound stopped. 5 Measurement of the reverberation time of rooms with reference to other 2.

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69 The reflected sound cursor was placed at a point on the curve approximately 5 dB down from the direct sound. The noise floor cursor was placed approximately 10dB above the ambient. By placing the cursors at these points, acoustical metrics are calculated within the Acoustic Tools software program, and results for Reverberation Time, Early Decay Time and C 80 are given, among others. An e xample of the placement of the cursors is given in Figure 3 1 5 Expanded method. T than the Traditional method to plot the least squares fit line. The direct sound cursor is kept in the same place as the Traditi onal Method however the reflected sound cursor is placed on the highest reflection just after the direct sound. The noise floor cursor is placed at the end of the decay, where the decay meets the noise floor, instead of being 10dB above it. These cursor positions are shown in Figure 3 1 6 Perceptual method. The method uses listening to determine when the direct sound stops and when the reverberant sound stops. The wav file used in the previous two methods is imported into the Audacity software program. The end note of the Trumpet Song and the last syllable of the Fema le Talker were analyzed. A 500, 1,000 and 4,000 Hertz octave filter was applied to the wav files independently, so that each octave band could be listened to separately. The wav file was played back via Sony MDR V600 Dynamic Stereo Headphones. To determ ine where the direct sound stopped, the wav file was played back at normal speeds and slower speeds. To determine where the reverberant sound stopped, the wav files were played back at speeds generally between 0.2 to 0.4 times slower than the original sou nd.

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70 Figure 3 1 5 Placement of cursors to derive acoustic metrics for the Traditional Method using t he end note of the Trumpet Song at 1,000 Hertz as an example Direct Sound Cursor Reflected Sound Cursor at 5dB from the Direct Sound Noise Floor Noise Floor Cursor at +10 dB above Noise Floor

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71 Figure. 3 1 6 Placements of cursors to derive acoustical metrics from the Expanded Method Noise Floor Cursor at Noise Floor Noise Floor Direct Sound Cursor Reflected Sound Cursor at first reflection after Direct Sound

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72 The wav files were listened to several times at different speeds to adequately determine where the direct and reverberant sound stopped. The times when the direct sound stopped and the reverberant soun d stopped were noted. The wav files were then moved to the time the direct sound was heard to stop. The Noise Floor cursor was placed on the time where the reverbera nt sound was heard to stop. The Noise Floor cursor was adjusted so that it could provide a visual least squares fit line on the decay curve. The RT, C 80 and EDT were determined from positioning the cursors at these Perceptual Win MLS method. involves using the time of the direct sound from the previous methods, and the time of the perceived end of the direct sound and end of reverberation. This method essentially took the data from the Perceptual Me thod and processed it using the WinMLS software program. The direct sound, end of direct sound and end of reverberation was noted for each octave band. A separate wav file was made that contained only the data between the times associated with the refle cted sound cursor and noise floor cursor. This new wav file was imported and analyzed with the WinMLS software to determine acoustic measures. Certain frequencies did not have enough signal level for the program to recognize and therefore no data was rec orded. F igures 3 1 9 through 3 20 show in detail each step of the process.

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73 Figure 3 1 7 End note of Trumpet Song with 1,000 Hertz octave filter applied to signal. Note the times, as they are used in the next step Direct Sound : 17.53 Where Direct Sound was heard to st op 17.69 Where Reflected Sound was heard to stop 18.30

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74 Figure 3 1 8 Cursor placement after filtering and listening to Trumpet Song stop chord. Note placement of cursors corresponds to times identified in Figure 3 1 7 Direct Sound 17.53 Where Direct Sound was heard to stop 17.69 Where Reflected Sound was heard to stop 18.30 Noise Floor

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75 Figure 3 1 9 New wav file made by clipping the top image between the Reflected Sound and Noise Floor cursors

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76 Figure 3 20 The new wav file from Figure 3 19 was run through WinMLS software program and a coustic metrics derived from this wav file RT Comparison The R everberation T imes derived from the natural acoustic sources were compared to the reverberation times derived from the scientifically calibrated sources. The Reverberation Times derived from the natural acoustic sources and scientifically calibrated sources were also compared to the Reverberation Times derived from the sources in the Pilot Study. The Reverberation Times derived from all three studies are shown in Figure 3 2 1 Data from the scientifically calibrated sources in the 4,000 Hertz octave band is included in the figure even though it was not analyzed in the Pilot Study. This data is meant to provide a frame of reference for the data derived from the natural acoust ic sources in the same frequency. There Reverberation Time data ranges from 0.71 to 1.80 seconds across the 500 1,000 and 4,000 Hertz octave bands.

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77 Figure 3 2 1 Reverberation Time comparison for Pilot Study, Study 1 and Study 2 in th e 500, 1000 and 4000 Hertz octave bands 0.6 1 1.4 1.8 2.2 2.6 3 500 1000 4000 Reverberation Time in Seconds Octave Band Center Frequency in Hertz Pilot Study: Dir corner sine sweep Pilot Study: Dir Front Sine Sweep Pilot Study: Mult Sine Sweep Dir Corner Pilot Study: Mult Sine Sweep Dir Front Pilot Study: Dir Front MLS Pilot Study: Dir Corner MLS Pilot Study: Balloon Pop MLS Pilot Study: Balloon POP AT Pilot Study: Female Talker Pilot Study: Piano Middle C Note Pilot Study: Piano Middle C Chord Pilot Study: Piano Song Pilot Study: Trumpet Song Study 1: Dir Front MLS Study 1: Dodec Front MLS Study 2: Traditional Method: Balloon Pop Study 2: Traditional Method: Female Talker Study 2: Traditional Method: Trumpet Song Study 2: Expanded Method: Balloon Pop Study 2: Expanded Method: Female Talker Study 2: Expanded Method: Trumpet Song Study 2: Perceptual Method: Balloon Pop Study 2: Perceptual Method: Female Talker Study 2: Perceptual Method: Trumpet Song Study 2: Perceptual WinMLS Method: Balloon Pop Study 2: Perceptual WinMLS Method: Female Talker Study 2: Perceptual WinMLS Method: Trumpet Song

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78 RT EDT Comparison Natural acoustic s ources By comparing the findings of this study to previous studies, one can attempt to show how the metrics derived from natural acoustic sources differ from metrics derived from scientifically calibrated sources. By subtracting the EDT from the RT derived from all 4 methods, it was found that the differences in the EDT and RT metrics are considerably larger than the differences of approximately 0.1 seconds found by Bradley. It should be noted that the metric described as the EDT for the natural acoustic sources is actually a relative value determined by obtaining the slope of the line that connects the direct sound cursor to the reflected sound cursor in Acoustic To ols. Using the Traditional method with the Female Talker stimulus, the differences between EDT and RT ranged from .37 to 2.16 seconds. When averaging both the left and right receivers over all 3 receiver positions, it was found that the RT was .12 in th e 4,000 Hertz octave band to .96 seconds in the 500 Hertz octave band longer than the EDT. Figure 3 2 2 Female Talker RT EDT analyzed using theTraditional Method -3 -2 -1 0 1 2 3 500 1000 4000 Difference of RT EDT in Seconds Octave Band Center Frequency in Hertz Female Talker RT EDT Traditional Method Traditional Right R1 Traditional Left R1 Traditional Right R2 Traditional Left R2 Traditional Right R3 Traditional Left R3

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79 The Female Talker source signal analyzed using the Extended Method resulted in differences in EDT and RT of .55 to 2.53 seconds, which is shown in Figure 3 2 3 When averaging the left and right side over all three receiver positions, the RT was greater than the EDT in the 500 Hertz octave band by 2.11 se conds. The averaged RT in the 1,000 Hertz octave band was greater than the EDT by 1.66 seconds. The averaged RT in the 4,000 Hertz octave band was greater than the EDT by 0.14 seconds. The Female Talker source signal analyzed with the Perceptual Method resulted in differences in the RT and EDT of between 0.28 and 2.2 seconds. When averaging the left and right side over all three receiver positions, the RT was greater than the EDT in the 500 Hertz octave band by 1.17 seconds. The averaged RT in the 1,0 00 Hertz octave band was greater than the EDT by 1.32 seconds. The averaged RT in the 4,000 Hertz octave band was greater than the EDT by 0.09 seconds. Figure 3 2 3 Female Talker RT EDT analyzed using the Expanded Method -3 -2 -1 0 1 2 3 500 1000 4000 Difference in RT EDT in Seconds Octave Band Center Frequency in Hertz Female Talker RT EDT Expanded Method Expanded Right R1 Expanded Left R1 Expanded Right R2 Expanded Left R2 Expanded Right R3 Expanded Left R3

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80 Figure 3 2 4 Female Talk er RT EDT analyzed using the Perceptual Method The Female Talker source analyzed with the Perceptual WinMLS Method resulted in d ifferences in the RT and EDT between 1.55 and 0.60 seconds. When averaging the left and right side over all three receiver positions, the RT was greater than the EDT in the 500 Hertz octave band by .003 seconds. The averaged RT in the 1,000 Hertz octave band was less than the EDT b y .17 seconds. The averaged RT in the 4,000 Hertz octave band was greater than the EDT by 0.01 seconds. Figure 3 2 5 Female Talker RT EDT analyzed using the Perceptual WinMLS Method -3 -2 -1 0 1 2 3 500 1000 4000 Difference in RT EDT in Seconds Octave Band Center Frequency in Hertz Female Talker RT EDT Perceptual Method Perceptual Right R1 Perceptual Left R1 Perceptual Right R2 Perceptual Left R2 Perceptual Right R3 Perceptual Left R3 -3 -2 -1 0 1 2 3 500 1000 4000 Difference in RT EDT in Seconds Octave Band Center Frequency in Hertz Female Talker RT EDT Perceptual WinMLS Method Perceptual WinMLS Right R1 Perceptual WinMLS Left R1 Perceptual WinMLS Right R2 Perceptual WinMLS Left R2 Perceptual WinMLS Right R3 Perceptual WinMLS Left R3

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81 The Female Talker source analyzed using the Expanded and Perc eptual methods resulted in differences in the RT EDT that were similar. The Female Talker source analyzed using the Perceptual WinMLS method resulted in the lowest differences in RT EDT. When using the Traditional Method with the Trumpet Song as a stimulus, the difference between RT and EDT varied from 1.26 to 2.59 seconds. When averaging the left and right side over all three receiver positions, the RT was greater than the EDT in the 500 Hertz octave band by 1.33 seconds. The averaged RT in the 1,000 Hertz octave band was greater than the EDT by 0.21 seconds. The averaged RT in the 4,000 Hertz octave band was greater than the EDT by 0.41 seconds. The Trumpet Song analyzed with the Expanded Method resulted in differences between RT and EDT vary ing from 0.88 to 2.5 seconds. When averaging the left and right side over all three receiver positions, the RT was greater than the EDT in the 500 Hertz octave band by 1.19 seconds. The averaged RT in the 1,000 Hertz octave band was greater than the EDT by 0.32 seconds. The averaged RT in the 4,000 Hertz octave band was greater than the EDT by 0.35 seconds. The Trumpet Song analyzed with Perceptual Method resulted in variances between the RT and EDT from 2.16 to 2.19 seconds. When averaging the left a nd right side over all three receiver positions, the RT was greater than the EDT in the 500 Hertz octave band by 0.36 seconds. The averaged RT in the 1,000 Hertz octave band was greater than the EDT by 0.41 seconds. The averaged RT in the 4,000 Hertz oct ave band was less than the EDT by 0.18 seconds.

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82 Figure 3 2 6 Trumpet Song RT EDT analyzed using theTraditional Method Figure 3 2 7 Trumpet Song RT EDT analyzed using the Expanded Method -3 -2 -1 0 1 2 3 500 1000 4000 Difference in RT EDT in Seconds Octave Band Center Frequency in Hertz Trumpet Song RT EDT Traditional Method Traditional Right R1 Traditional Left R1 Traditional Right R2 Traditional Left R2 Traditional Right R3 Traditional Left R3 -3 -2 -1 0 1 2 3 500 1000 4000 Difference in RT EDT in Seconds Octave Band Center Frequency in Hertz Trumpet Song RT EDT Expanded Method Expanded Right R1 Expanded Left R1 Expanded Right R2 Expanded Left R2 Expanded Right R3 Expanded Left R3

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83 Figure 3 2 8 Trumpet Song RT EDT analyzed using the Perceptual Method The Trumpet Song analyzed using the Perceptual WinMLS Method resulted in differences in the RT and EDT of between 0.63 and 0.52 seconds. When averaging the left and right side over all three receiver positions, the RT was less than the EDT in the 500 Hertz octave band by 0.25 seconds. The averaged RT in the 1,000 Hertz octave band was greater than the EDT by 0.17 seconds. The averaged RT in the 4,000 Hertz octave band was less than the EDT by 0.04 seconds. Similar to the F emale Talker the Trumpet Song resulted in similar differences in the RT EDT using the Expanded and Perceptual Method. The Trumpet Song analyzed using the Perceptual WinMLS also resulted in the lowest differences in RT EDT. The Balloon Pop s were also analyzed using the same methods that were used to analyze the natural acoustic stimuli. They were used as they provide an approximately broadband stimulus that excites the frequencies that are analyzed in this paper. Although balloons have been fou nd to not meet the ISO 3382 standard for being an -3 -2 -1 0 1 2 3 500 1000 4000 Difference in RT EDT in Seconds Octave Band Center Frequency in Hertz Trumpet Song RT EDT Perceptual Method Perceptual Right R1 Perceptual Left R1 Perceptual Right R2 Perceptual Left R2 Perceptual Right R3 Perceptual Left R3

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84 omnidirectional source they were used in this study as a comparison against the natural acoustic sources. The Balloon Pop analyzed with the Traditional Method resulted in differences in RT and EDT rangin g from 1.88 to 1.55 seconds. When averaging the left and right side over all three receiver positions, the RT was greater than the EDT in the 500 Hertz octave band by 0.61 seconds. The averaged RT in the 1,000 Hertz octave band was greater than the EDT by 0.87 seconds. The averaged RT in the 4,000 Hertz octave band was greater than the EDT by 0.79 seconds. The Balloon Pop analyzed with the Expanded Method resulted in differences between RT and EDT varying from 0.38 to 2.1 seconds. When averaging the left and right side over all three receiver positions, the RT was greater than the EDT in the 500 Hertz octave band by 1.17 seconds. The averaged RT in the 1,000 Hertz octave band was greater than the EDT by 1.59 seconds. The averaged RT in the 4,000 Her tz octave band was greater than the EDT by 1.14 seconds. Figure 3 2 9 Trumpet Song RT EDT analyzed using the Perceptual WinMLS Method J. Patynen, B F. G. Katz, and T The Journal of the Acoustical Society of America 129 ( 2011): 32. -3 -2 -1 0 1 2 3 500 1000 4000 Difference in RT EDT in Seconds Octave Band Center Frequency in Hertz Trumpet Song RT EDT Perceptual WinMLS Method Perceptual WinMLS Right R1 Perceptual WinMLS Left R1 Perceptual WinMLS Right R2 Perceptual WinMLS Left R2 Perceptual WinMLS Right R3 Perceptual WinMLS Left R3

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85 Figure 3 30 Balloon Pop RT EDT analyzed using the Traditional Method Figure 3 3 1 Balloon Pop RT EDT analyzed using the Expanded Method The Balloon Pop analyzed with the Perceptual Method resulted in differences in the RT and EDT of between 2.56 and 2.06 seconds. When averaging the left and right side over all three receiver positions, the RT was greater than the EDT in the 500 Hertz octave band by 1.60 seconds. The averaged RT in the 1,000 Hertz octave band was -3 -2 -1 0 1 2 3 500 1000 4000 Difference in RT EDT in Seconds Octave Band Center Frequency in Hertz Balloon Pop RT EDT Traditional Method Traditional Right R1 Traditional Left R1 Traditional Right R2 Traditional Left R2 Traditional Right R3 Traditional Left R3 -3 -2 -1 0 1 2 3 500 1000 4000 Difference in RT EDT in Seconds Octave Band Center Frequency in Hertz Balloon Pop RT EDT Expanded Method Expanded Right R1 Expanded Left R1 Expanded Right R2 Expanded Left R2 Expanded Right R3 Expanded Left R3

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86 greater than the EDT by 1.71 seconds. The averaged RT in the 4,000 Hertz octave band was greater than the EDT by 0.57 seconds. F igure 3 3 2 Balloon Pop RT EDT analyzed using the Perceptual Method The Balloon Pop source analyzed with the Perceptual WinMLS Method resulted in differences in the RT and EDT of between 0.13 and 0.36 seconds. When averaging the left and right side ove r all three receiver positions, the RT was greater than the EDT in the 500 Hertz octave band by 0.06 seconds. The averaged RT in the 1,000 Hertz octave band was greater than the EDT by 0.08 seconds. The averaged RT in the 4,000 Hertz octave band was less than the EDT by 0.01 seconds. For the Traditional, Expanded and Perceptual Methods, the EDT is regulated by where the Direct Sound cursor is placed on the curve. For the natural acoustic sources, the entire sound file had to be used when analyzing the decay curve. Because of this, even slight variations in the placement of the cursors could result in large differences in the EDT -3 -2 -1 0 1 2 3 500 1000 4000 Difference in RT EDT in Seconds Octave Band Center Frequency in Hertz Balloon Pop RT EDT Perceptual Method Perceptual Right R1 Perceptual Left R1 Perceptual Right R2 Perceptual Left R2 Perceptual Right R3 Perceptual Left R3

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87 Figure 3 3 3 Balloon Pop RT EDT analyzed using the Perceptual WinMLS Method A clipped file of just the end note could not be analyzed using Acoustic Tools because the signal energy was spread out so much that the decay slope no longer had a 45 o slope (whi ch is preferred for calculated Reverberation T ime) The slope for the cl ipped file was approximately 165 o and therefore not ideal to analyze. The averaged Balloon Pop data analyzed using the Perceptual WinMLS Method resulted in the lowest RT EDT differences in the 500, 1,000 and 4,000 hertz octave bands. Th ese low differences ar e most likely due to the B alloon P op having a steady, easily discernible decay curve, and broadband spectrum The low differences for the B alloon P op analyzed using the Perceptual WinMLS method are also most likely due to the fact that the B alloon P op signal was run through the WinMLS computer software program whose analysis techniques are internally consistent and not based on human input Overall, the differences in RT EDT ranged from 2.5 to 2.59 seconds using the natural acoustic sources. The di fferences in RT E DT for the scientifically calibrated sources ranged from .19 to 0.32 seconds. The differences in RT EDT for scientifically calibrated are approximately 8 times shorter than the differences in RT EDT in the natural acoustic -3 -2 -1 0 1 2 3 500 1000 4000 Difference in RT EDT in Seconds Octave Band Center Frequency in Hertz Balloon Pop RT EDT Perceptual WinMLS Method Perceptual WinMLS Right R1 Perceptual WinMLS Left R1 Perceptual WinMLS Right R2 Perceptual WinMLS Left R2 Perceptual WinMLS Right R3 Perceptual WinMLS Left R3

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88 sources. T find significant differences in the RT and EDT values 5 Scientifically calibrated sources Values for EDT and RT using the scientifically calibrated methods were also compared. It was found that with EDT and RT measurements derived from acoustical measurements using the o mnidirectional loudspeaker in the first receiver position, the EDT values were generally higher than RT values in the 500 Hertz octave band. However, in the 1,000 and 4,000 Hertz octave bands, the EDT values were slightly lower than the RT values. Overall, the differences from subtracting EDT from RT with both loudspeaker types are similar, and ranged from + .01 to 0 .3 seconds. This is a much smaller variation th an the alternative source signals, however still a larger variation than what Kwon and Jordan have found. Figure 3 3 4 Averaged MLS measurements dervied from the directional loudspeaker subtracting EDT from RT at receiver locations R1, R2 and R3 5 Youngmin Balcony Acoustics 2006), 5 0 53. -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40 500 1000 4000 Difference in RT EDT in Seconds Octave Band Center Frequency in Hertz Directional RT EDT Average Dir R1 Avg Dir R2 Avg Dir R3 Avg

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89 Figure 3 3 5 Averaged MLS measurements dervied from the omnidirectional loudspeaker subtracting EDT from RT at receiver locations R1, R2 and R3 Reverberation Time Comparison Results The R everberation T ime data f r om methods 1 4 were normalized to the average R everberation T ime values from acoustical measurements made using the MLS signal at each receiver position. The average MLS values became the 0 and the values derived for the natural acoustic sources were plotted on the graphs with the averag e MLS values as the 0. Negative numbers indicated the values derived from the natural acoustic sources were below the average MLS data, while positive values indicated values higher than the average MLS data. This allows us to determine how different the natural acoustic sources are compared to the traditional scientifically calibrated sources. The normalized R everberation T imes were then compared by source, method and receiver position. It was found that the Trumpet Song had longer reverberation times t han the Female Talker Figure 3 3 6 shows graphs of the Female Talker and Trumpet Song Reverberation Time data normalized to the Average MLS data for the 1 st receiver posit ion. The RT data for the Trumpet S ong are closer to the normalized value of 0, and therefore have higher values than the Female Talker data. The R everberation -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 500 1000 4000 Difference in RT EDT in Seconds Octave Band Center Frequency in Hertz Omnidirectional Loudspeaker RT EDT Average Dodec R1 Avg Dodec R2 Avg Dodec R3 Avg

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90 T imes derived from the Balloon Pop impulses tended to fall between the Female Talker and Trumpet Song Figure 3 3 6 Female Talker and Trumpet Song Reverberation Time s normalized to average MLS data The R everberation T imes derived using the Balloon Pop as the source signal resulted in all 4 methods having similar v alues. The similar values in RT are attributed to the B alloon P op having high sound energy, having nearly equal energy per octave band and that it has nearly an omnidirectional dispersion pattern which uniformly excites the reverberant field in the room. T he R everberation T imes derived from the natural acoustic source signals were different between methods an d receiver position. The differences in RT between the Female Talker and Trumpet Song are most likely due to the limited sound energy, the sources exciting only limited frequencies and having di rectional characteristics from the directional loudspeaker Figure 3 3 7 shows the normalized RT data for the Balloon Pop revealing similar values for each method at each receiver position -3 -2 -1 0 1 2 3 500 1000 4000 Normalized Reverberation Time in Seconds Octave Band Center Frequency in Hertz Female Talker RT Normalized to Average MLS Receiver 1 Traditional Right R1 Traditional Left R1 Expanded Right R1 Expanded Left R1 Perceptual Right R1 Perceptual Left R1 Perceptual WinMLS Right R1 Perceptual WinMLS Left R1 -3 -2 -1 0 1 2 3 500 1000 4000 Normalized Reverberation Time in Seconds Octave Band Center Frequency in Hertz Trumpet Song RT Normalized to Average MLS Receiver 1 Traditional Right R1 Traditional Left R1 Expanded Right R1 Expanded Left R1 Perceptual Right R1 Perceptual Left R1 Perceptual WinMLS Right R1 Perceptual WinMLS Left R1

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91 For the natural acoustic sources, the Expanded and Perceptual Methods resulted in similar values. Figure 3 3 8 shows graphs of the Female Talker and Trumpet Song analyzed using the Expanded and Perceptual Methods. Figure 3 3 7 Balloon Pop source graphs showing similar RT values across receiver positions and methods -3 -2 -1 0 1 2 3 500 1000 4000 Normalized Reverberatioin Time in Seconds Octave Band Center Frequency in Hertz Balloon Pop RT Normalized to Average MLS Receiver 1 Traditional Right R1 Traditional Left R1 Expanded Right R1 Expanded Left R1 Perceptual Right R1 Perceptual Left R1 Perceptual WinMLS Right R1 Perceptual WinMLS Left R1 -3 -2 -1 0 1 2 3 500 1000 4000 Normalized Reverberation Time in Seconds Octave Band Center Frequency in Hertz Balloon Pop RT Normalized to Average MLS Receiver 2 Traditional Right R2 Traditional Left R2 Expanded Right R2 Expanded Left R2 Perceptual Right R2 Perceptual Left R2 Perceptual WinMLS Right R2 Perceptual WinMLS Left R2 -3 -2 -1 0 1 2 3 500 1000 4000 Normalized Reverberation Time in Seconds Octave Band Center Frequency in Hertz Balloon Pop RT Normalized to Average MLS Receiver 3 Traditional Right R3 Traditional Left R3 Expanded Right R3 Expanded Left R3 Perceptual Right R3 Perceptual Left R3 Perceptual WinMLS Right R3 Perceptual WinMLS Left R3

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92 Figure 3 3 8 Graphs of Female Talker Normalized Reverberation Times using Expanded and Perceptual Methods, which result in similar values Figure 3 3 9 Graphs of Trumpet S ong Normalized Reverberation Times using Expanded and Perceptual Methods, which result in similar values -3 -2 -1 0 1 2 3 500 1000 4000 Normalized Reverberation Time in Seconds Octave Band Center Frequency in Hertz Female Talker RT Normalized to Average MLS Expanded Method Expanded Right R1 Expanded Left R1 Expanded Right R2 Expanded Left R2 Expanded Right R3 Expanded Left R3 -3 -2 -1 0 1 2 3 500 1000 4000 Normalized Reverberation Time in Seconds Octave Band Center Frequency in Hertz Female Talker RT Normalized to Average MLS Perceptual Method Perceptual Right R1 Perceptual Left R1 Perceptual Right R2 Perceptual Left R2 Perceptual Right R3 Perceptual Left R3 -3 -2 -1 0 1 2 3 500 1000 4000 Normalized Reverberation Time in Seconds Octave Band Center Frequency in Hertz Trumpet Song RT Normalized to Average MLS Expanded Method Expanded Right R1 Expanded Left R1 Expanded Right R2 Expanded Left R2 Expanded Right R3 Expanded Left R3 -3 -2 -1 0 1 2 3 500 1000 4000 Normalized Reverberation Time in Seconds Octave Band Center Frequency in Hertz Trumpet Song RT Normalized to Average MLS Perceptual Method Perceptual Right R1 Perceptual Left R1 Perceptual Right R2 Perceptual Left R2 Perceptual Right R3 Perceptual Left R3

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93 After analyzing the Trumpet Song spectrograph using Acoustic Tools software, it was found that it contained high energy levels from 5 00, 6 30 1, 250 1, 600, 2,000 2,500 and 3,150 Hertz. The Female Talker was analyzed in the same way, and it was determined that the signal had much less energy in all octave bands, and only had higher energy levels between 6, 300 and 10,000 Hertz. This is due to th e stop chord Figure 3 40 shows the spectrograph of the last syllable of the Female Talker audio file. Figure 3 40 Spectrograph of the Female Talker last syllable with concentration of sound energy in the 6,500 to 9,200 Hertz octave bands analysis more difficult because there were not high energy levels in the octave bands analyzed. The Trumpet Song had more energy in the octave bands that were analyzed than the Female Talker did, which resulted in higher sound

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94 levels and higher measured R everberation T imes. The spectrograph for the Trumpet Song is shown in Figure 3 4 1 Figure 3 4 1 Spectrograph of the Trumpet Song end note. The Trumpet Song has more concentrated sound energy in many frequencies than the Female Talker The Balloon Pop h ad a more broadband signal and loud sound level, and was a more omnidirectional source which results in small differences in the R everberation T imes between the right and left receiver. Figure 3 4 2 shows the spectrograph of the Balloon Pop source signal. The natural acoustic sources have strong signals in limited frequencies, have weaker source levels and have more variation in the right and left receiver positions Overall, the R everberation T imes for the Balloon Pop s show less variation between

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95 method s, receiver positions and left and right receivers than th e natural acoustic sources due to consistency and strength of the source Figure 3 4 2 Spectrograph of the Balloon Pop. The solid decay of green, yellow, red and orange indicate very strong levels across all frequencies Much of the Reverberation Time data fell below the average MLS data. In fact, of the 216 receivers, 86 % were below the average. Of the data that were above the average MLS, 63% were less than or equal to 0.2 seconds greater than the average. The Trumpet Song had the most data above the average MLS data, with 60% above the average. The Female Talker accounted for 27% of the data above the average MLS and the Balloon Pop accounted for just 13%.

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96 Early Decay Time Comparison Results The Early Decay Times for all 4 methods were normalized to the average EDT values derived from acoustical measurements using the MLS signal. Early Decay Time (EDT) is typically defined as the time it takes a source level to decay by 10, 15 or 20 dB H owe ver, for this study, the EDT was calculated with the Acoustic Tools software by extrapolating from the slope between the direct sound cursor and the reflected sound cursor. E ach method had different placements of these cursors, and therefore vary ing EDT values could have been the result of the method that was used It was found that the Traditional, Perceptual and Perceptual WinMLS methods resulted in similar EDT values for the Female Talker source. Figure 3 4 3 shows these three methods. Receiver positions 1 and 3 had similar EDT values in the 500 and 4,000 Hertz octave bands, which are shown in Figure 3 4 4 Receiver position 2 had slightly higher EDT values than the receiver positions 1 and 3 When using the Trumpet Song as the sound sou rce, it was found that the Traditional and Perceptual WinMLS methods had similar results. The graphs for these methods are shown in Figure 3 4 5 Interestingly, the Expanded and Perceptual methods had differences in the left and right signals at receiver positions 1 3 There are variations between left and right receiver signals with the Trumpet Song signal shown in Figure 3 4 6 These variations are most likely due to the fact that the source signal is slightly different between right and left, and the source is listened to to determine where the direct and reflected sounds start and stop. The left and right signals are different and the Perceptual method highlights these differences. The graphs for these are shown in Figure 3 4 6

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97 Figure 3 4 3 Female Talker source analyzed with Traditional, Perceptual and Perceptual WinMLS methods resulting in similar normalized EDT values -3 -2 -1 0 1 2 3 500 1000 4000 Normalzed EDT in Seconds Octave Band Center Frequency in Hertz Female Talker EDT Normalized to Average MLS Traditional Method Traditional Right R1 Traditional Left R1 Traditional Right R2 Traditional Left R2 Traditional Right R3 Traditional Left R3 -3 -2 -1 0 1 2 3 500 1000 4000 Normalzed EDT in Seconds Octave Band Center Frequency in Hertz Female Talker EDT Normalized to Average MLS Perceptual Method Perceptual Right R1 Perceptual Left R1 Perceptual Right R2 Perceptual Left R2 Perceptual Right R3 Perceptual Left R3 -3 -2 -1 0 1 2 3 500 1000 4000 Normalzed EDT in Seconds Octave Band Center Frequency in Hertz Female Talker EDT Normalized to Average MLS Perceptual WinMLS Method Perceptual WinMLS Right R1 Perceptual WinMLS Left R1 Perceptual WinMLS Right R2 Perceptual WinMLS Left R2 Perceptual WinMLS Right R3 Perceptual WinMLS Left R3

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98 Figure 3 4 4 Female Talker Nor malized EDT values for Receiver Positions 1 and 3 Figure 3 4 5 Trumpet Song Normalized EDT values for Traditional and Perceptual WinMLS methods -3 -2 -1 0 1 2 3 500 1000 4000 Normalzed EDT in Seconds Octave Band Center Frequency in Hertz Female Talker EDT Normalized to Average MLS Receiver 1 Traditional Right R1 Traditional Left R1 Expanded Right R1 Expanded Left R1 Perceptual Right R1 Perceptual Left R1 -3 -2 -1 0 1 2 3 500 1000 4000 Normalzed EDT in Seconds Octave Band Center Frequency in Hertz Female Talker EDT Normalized to Average MLS Receiver 3 Traditional Right R3 Traditional Left R3 Expanded Right R3 Expanded Left R3 Perceptual Right R3 Perceptual Left R3 -3 -2 -1 0 1 2 3 500 1000 4000 Normalzed EDT in Seconds Octave Band Center Frequency in Hertz Trumpet Song EDT Normalized to Average MLS Traditional Method Traditional Right R1 Traditional Left R1 Traditional Right R2 Traditional Left R2 Traditional Right R3 Traditional Left R3 -3 -2 -1 0 1 2 3 500 1000 4000 Normalzed EDT in Seconds Octave Band Center Frequency in Hertz Trumpet Song EDT Normalized to Average MLS Perceptual WinMLS Method Perceptual WinMLS Right R1 Perceptual WinMLS Left R1 Perceptual WinMLS Right R2 Perceptual WinMLS Left R2 Perceptual WinMLS Right R3 Perceptual WinMLS Left R3

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99 Figure 3 4 6 Trumpet Song Normalized EDT values for Expanded and Perceptual methods The Trumpet Song had more variability in EDT values than the Female Talker Figure 3 4 7 shows graphs of the Female Talker and Trumpet Song receiver position 3 The Trumpet Song has more variations, especially between the right and left receivers than the Female Talker Th ese variations between left and right receivers with the Trumpet Song source could be caused because the distance from source to receiver is increased and therefore the sound is being affected by the room surfaces more than the receivers that obtain more direct sound because they are closer to the source The left receiver has hi gher EDT values than the right, perhaps due to reflections that focus more sound energy to the left ear due to its proximity to the wall surface. Interestingly, only the Balloon Pop resulted in similar normalized EDT values using the Expanded and Perceptual approach (which had a tendency to be similar when analyizing the RT and C 80 ). Figure 3 4 8 shows graphs of these 2 methods. -3 -2 -1 0 1 2 3 500 1000 4000 Normalzed EDT in Seconds Octave Band Center Frequency in Hertz Trumpet Song EDT Normalized to Average MLS Expanded Method Expanded Right R1 Expanded Left R1 Expanded Right R2 Expanded Left R2 Expanded Right R3 Expanded Left R3 -3 -2 -1 0 1 2 3 500 1000 4000 Normalzed EDT in Seconds Octave Band Center Frequency in Hertz Trumpet Song EDT Normalized to Average MLS Perceptual Method Perceptual Right R1 Perceptual Left R1 Perceptual Right R2 Perceptual Left R2 Perceptual Right R3 Perceptual Left R3

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100 When analyzing the Balloon Pop the Perceptual WinMLS method resulted in normalized EDT values that were similar to the average MLS EDT values. A graph of this data is shown in Figure 3 4 9 Figure 3 4 7 Graphs showing large variation in left and right receiver normalized EDT values for Trumpet Song c ompared to fairly consistent Female Talker values For the Balloon Pop source, receiver position 1 had the most uniform normalized EDT values across the 4 methods. As the receiver moved farther from the source, variations in EDT values were present between the left and right receivers. Figure 3 50 shows the normalized EDT values in receiver position s 1 and 3, where the differences between left and right are more prominent. -3 -2 -1 0 1 2 3 500 1000 4000 Normalzed EDT in Seconds Octave Band Center Frequency in Hertz Female Talker EDT Normalized to Average MLS Receiver 3 Traditional Right R3 Traditional Left R3 Expanded Right R3 Expanded Left R3 Perceptual Right R3 Perceptual Left R3 Perceptual WinMLS Right R3 Perceptual WinMLS Left R3 -3 -2 -1 0 1 2 3 500 1000 4000 Normalzed EDT in Seconds Octave Band Center Frequency in Hertz Trumpet Song EDT Normalized to Average MLS Receiver 3 Traditional Right R3 Traditional Left R3 Expanded Right R3 Expanded Left R3 Perceptual Right R3 Perceptual Left R3 Perceptual WinMLS Right R3 Perceptual WinMLS Left R3

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101 Figure 3 4 8 Graphs of Balloon Pop analyzed with Expanded and Perceptual methods resulting in similar normalized EDT values Figure 3 4 9 Balloon Pop analyzed using the Perceptual WinMLS method resulting in EDT values that are centered around average MLS data -3 -2 -1 0 1 2 3 500 1000 4000 Normalzed EDT in Seconds Octave Band Center Frequency in Hertz Balloon Pop EDT Normalized to Average MLS Expanded Method Expanded Right R1 Expanded Left R1 Expanded Right R2 Expanded Left R2 Expanded Right R3 Expanded Left R3 -3 -2 -1 0 1 2 3 500 1000 4000 Normalzed EDT in Seconds Octave Band Center Frequency in Hertz Balloon Pop EDT Normalized to Average MLS Perceptual Method Perceptual Right R1 Perceptual Left R1 Perceptual Right R2 Perceptual Left R2 Perceptual Right R3 Perceptual Left R3 -3 -2 -1 0 1 2 3 500 1000 4000 Normalzed EDT in Seconds Octave Band Center Frequency in Hertz Balloon Pop EDT Normalized to Average MLS Perceptual WinMLS Method Perceptual WinMLS Right R1 Perceptual WinMLS Left R1 Perceptual WinMLS Right R2 Perceptual WinMLS Left R2 Perceptual WinMLS Right R3 Perceptual WinMLS Left R3

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102 Much of the EDT data fell below the average MLS data. Interestingly, as with the Reverberation Time, of the 216 receivers, 86% were below the average. However, of the 31 receivers that were above the average MLS data, only 32% were less than or equal to 0.2 seconds above the average. The Trumpet Song had the most data points above the average, with 58% of the data above the average MLS data. The Balloon Pop had 32% and the Female Talker had only 10% of the data with values above the average MLS data. C 8 0 Comparison Results The C 80 values for methods 1 4 were normalized to the average C 80 values derived from acoustical measurements using an MLS signal. These normalized values were compared by method and receiver position, similar to the RT comparison described above. It was found that the Trumpet Song resulted in lower C 80 values than th e Female Talker in general. The Balloon Pop had similar left and right receiver values in all receiver positions and across all methods; however the T rumpet Song and the Female Talker did not. The balloon is a more broadband and louder source that excite s the room more evenly than the speech or music. Like the R everberation T ime analysis, the Balloon Pop shows little variation in C 80 values between method, receiver position and left and right receiver. Again, for both the Female Talker and Trumpet Song C 80 values were similar when analyzed using the Expanded and Perceptual methods. Figures 3 5 1 through 3 5 2 show graphs of the two natural acoustic sources analyzed using the Expanded and Perceptual methods. Similar to the normalized Reverberation Time results, the B allon P op again had similar C 80 values across all 4 methods and receiver positions which is shown in Figure 3 5 3

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103 Figure 3 50 Balloon Pop source at receiver positions 1 and 3, showing differences in left and right receivers as the receiver position moves farther from the source Figure 3 5 1 Graphs of Female Talker Normalized C 80 values using Expanded and Perceptual Methods, which result in similar values -3 -2 -1 0 1 2 3 500 1000 4000 Normalzed EDT in Seconds Octave Band Center Frequency in Hertz Balloon Pop EDT Normalized to Average MLS Receiver 1 Traditional Right R1 Traditional Left R1 Expanded Right R1 Expanded Left R1 Perceptual Right R1 Perceptual Left R1 Perceptual WinMLS Right R1 Perceptual WinMLS Left R1 -3 -2 -1 0 1 2 3 500 1000 4000 Normalzed EDT in Seconds Octave Band Center Frequency in Hertz Balloon Pop EDT Normalized to Average MLS Receiver 3 Traditional Right R3 Traditional Left R3 Expanded Right R3 Expanded Left R3 Perceptual Right R3 Perceptual Left R3 Perceptual WinMLS Right R3 Perceptual WinMLS Left R3 -8 -4 0 4 8 12 500 1000 4000 Normalized C 80 in decibels Octave Band Center Frequency in Hertz Female Talker C 80 Normalized to Average MLS Expanded Method Expanded Right R1 Expanded Left R1 Expanded Right R2 Expanded Left R2 Expanded Right R3 Expanded Left R3 -8 -4 0 4 8 12 500 1000 4000 Normalized C 80 in decibels Octave Band Center Frequency in Hertz Female Talker C 80 Normalized to Average MLS Perceptual Method Perceptual Right R1 Perceptual Left R1 Perceptual Right R2 Perceptual Left R2 Perceptual Right R3 Perceptual Left R3

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104 Figure 3 5 2 Graphs of Trumpet Song Normalized C 80 values using Expanded and Perceptual Methods, which result in similar values The natural acoustic sources do not excite the room uniformly across all octave bands, and as such some frequency bands have lower le vels than others. The series of reflections in the first 80 ms varies greatly depending upon the source type and receiver position and musical sources played through a violin structure. He found large variations in C 80 values (from 4.6 to 5.9 at the 1000 Hertz octave bands) when source positions varied. 6 6 D. -8 -4 0 4 8 12 500 1000 4000 Normalized C 80 in decibels Octave Band Center Frequency in Hertz Trumpet Song C 80 Normalized to Average MLS Expanded Method Expanded Right R1 Expanded Left R1 Expanded Right R2 Expanded Left R2 Expanded Right R3 Expanded Left R3 -8 -4 0 4 8 12 500 1000 4000 Normalized C 80 in decibels Octave Band Center Frequency in Hertz Trumpet Song C 80 Normalized to Average MLS Perceptual Method Perceptual Right R1 Perceptual Left R1 Perceptual Right R2 Perceptual Left R2 Perceptual Right R3 Perceptual Left R3

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105 Figure 3 5 3 Graphs of normalized C80 values for Balloon Pop source for the 3 receiver positions -8 -4 0 4 8 12 500 1000 4000 Normalized C80 in decibels Octave Band Center Frequency in Hertz Balloon Pop C80 Normalized to Average MLS Receiver 1 Traditional Right R1 Traditional Left R1 Expanded Right R1 Expanded Left R1 Perceptual Right R1 Perceptual Left R1 Perceptual WinMLS Right R1 -8 -4 0 4 8 12 500 1000 4000 Normalized C80 in decibels Octave Band Center Frequency in Hertz Balloon Pop C80 Normalized to Average MLS Receiver 2 Traditional Right R2 Traditional Left R2 Expanded Right R2 Expanded Left R2 Perceptual Right R2 Perceptual Left R2 Perceptual WinMLS Right R2 Perceptual WinMLS Left R2 -8 -4 0 4 8 12 500 1000 4000 Normalized C80 in decibels Octave Band Center Frequency in Hertz Balloon Pop C80 Normalized to Average MLS Receiver 3 Traditional Right R3 Traditional Left R3 Expanded Right R3 Expanded Left R3 Perceptual Right R3 Perceptual Left R3 Perceptual WinMLS Right R3 Perceptual WinMLS Left R3

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106 T he T rumpet Song source has longer Reverberation T imes than the Female Talker and lower C 80 values These findings beration that is to say, the room is ver y dead the music will be very clear and C 80 will have a large positive value (in decibels). If the reverberation is large such as exists in a huge cathedral the music will be unclear and C 80 7 The C 80 graphs also indicate a large range in C 80 values, especially among the natural acoustic source indicating that there was much variation in the C 80 values when considering different receive r positions 8 As with the RT and EDT, much of the data was below the average MLS data. Of the 216 receiver, 73% were below the average. Of the 58 data points that were above the average, 41% were less than or equal to 1.38dB above the average, which i s the Just Noticeable Difference value used in the study. The Female Talker had the most data points above the average, accounting for 43% of the all data above the average. The Trumpet Song accounted for 36% of the data above the average. The Balloon P op had the least, with only 21% of data above the average. Just Noticeable Differences The Just Noticeable Differences for the RT and C 80 derived from acoustical measurements made using the alternative source signals were compared. It was 7 L L Beranek, Concert and Opera Halls: How They Sound (Woodbury, NY: Published for the Acoustical Society of America through the Ameri can Institute of Physics, 1996) 478. 8 Kwon, 54 56.

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107 d greater variation than C 80 Reverberation t ime j ust n oticeable d ifferences Table 3 1. J ust n oticeable d ifference in r everberation t ime ranges grouped by method Just Noticeable Difference Ranges for Reverberation Time by Method Female Talker Trumpet Song Balloon Pop Directional Speaker Omni directional Speaker Traditional 2 20 0 10 1 8 0 1 0 2 Expanded 0 16 0 6 0 6 Perceptual 0 15 0 18 0 6 Perceptual WinMLS 6 22 1 21 0 3 The JND ranges for the Reverberation Times derived from the scientifically calibrated sources were between 0 and 1 for the directional loudspeaker and 0 and 2 for the omnidirectional loudspeaker. The lower JND values and smaller range suggest more consistency in the data derived from the scientifically calibrated sources. Compared to the scientifically calibrated sources, the Female Talker and Trumpet Song had JND values that were up to 11 times t he JND values derived from the scientifically calibrated sources. T he F emale T alker had a higher R everbe ration T ime JND range than the T rumpet Song and the B alloon P op having the lowest JND range (from 0 8 largest range of JND values (1 8) for the B alloon P op source. For the F emale T alker source, the Traditional and Pe r ceptual

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108 WinMLS methods resulted in the highest JND values. For both the F emale T alker and the T rumpet S ong, the Expanded and Perceptual met hods had similar JND values in the 4,000 Hertz octave band, shown in Figures 3 5 4 through 3 5 5 Figure 3 5 4 Graphs showing Female Talker having similar JND values in the 4,000 Hertz octave band for Expanded and Perceptual methods Figure 3 5 5 Graphs showing Trumpet Song having similar JND values in the 4,000 Hertz octave band for Expanded and Perceptual methods 0 5 10 15 20 25 500 1000 4000 Just Noticeable Difference in Reverberation Time Octave Band Center Frequency in Hertz Female Talker JND for RT Expanded Method Expanded Right R1 Expanded Left R1 Expanded Right R2 Expanded Left R2 Expanded Right R3 Expanded Left R3 0 5 10 15 20 25 500 1000 4000 Just Noticeable Difference in Reverberation Time Octave Band Center Frequency in Hertz Female Talker JND for RT Perceptual Method Perceptual Right R1 Perceptual Left R1 Perceptual Right R2 Perceptual Left R2 Perceptual Right R3 Perceptual Left R3 0 5 10 15 20 25 500 1000 4000 Just Noticeable Difference in Reverberation Time Octave Band Center Frequency in Hertz Trumpet Song JND for RT Expanded Method Expanded Right R1 Expanded Left R1 Expanded Right R2 Expanded Left R2 Expanded Right R3 Expanded Left R3 0 5 10 15 20 25 500 1000 4000 Just Noticeable Difference in Reverberation Time Octave Band Center Frequency in Hertz Trumpet Song JND for RT Perceptual Method Perceptual Right R1 Perceptual Left R1 Perceptual Right R2 Perceptual Left R2 Perceptual Right R3 Perceptual Left R3

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109 The B alloon P op resulted in JND values that were similar using the Expanded and Perceptual methods, and the Perceptual WinMLS method resulted in the lowest JND values. Table 3 2. J ust n oticeable d ifference in r everberation t ime ranges grouped by receiver position Just Noticeable Difference Ranges for Reverberation Time by Receiver Female Talker Trumpet Song Balloon Pop Directional Speaker Omni directional Speaker Receiver 1 4 22 0 19 0 6 0 0 2 Receiver 2 0 21 0 18 0 8 0 0 1 Receiver 3 0 19 0 21 0 6 0 1 0 2 The natural acoustic sources of the F emale T alker and T rumpet S ong had similar JND for RT values at each receiver position while the B alloon P op had significantly lower JND values. However, when compared to the scientifically calibrated sources using the directional and omnidirectional (of 0 2 JND), the three additional sou rces have much larger RT E arly d ecay t ime j ust n oticeable d ifferences It was found that with both the Female Talker and the Trumpet Song that the position was farther away from the source. However, the con verse was true with the Balloon Pop the receiver position was closer to the source.

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110 When using the Female Talker source, the Traditional and Perceptual methods had similar results. Table 3 3. J ust n oticeable d ifference ranges for e arly d ecay t ime grouped by method Just Noticeable Difference Ranges for Early Decay Time by Method Female Talker Trumpet Song Balloon Pop Directional Speaker Omni directional Speaker Traditional 6 -19 1 -17 2 -21 0 0 4 Expanded 3 -19 0 -17 1 -20 Perceptual 2 -18 1 -27 2 -20 Perceptual WinMLS 1 -17 0 -16 0 -3 For all 4 methods, the JND values were higher in the 500 and 1,000 Hertz octave bands than the 4,000 Hertz octave band. It is assumed this is due to the fact that the Female Talker has more energy in the 4,000 Hertz octave band and therefore produces a mo re measureable signal. For the Trumpet Song source signal, the Expanded and Perceptual methods resulted in similar values, with the exception of the Perceptual Right Receiver position 3 which resulted in a JND of 27, which is shown in Table 3 4. The Pe rceptual WinMLS method resulted in the lowest EDT JND values for the Trumpet Song source. Similar to the Trumpet Song source, the Balloon Pop source processed with the Expanded and Perceptual methods resulted in similar values, shown in Figure 3 5 6

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111 Tabl e 3 4. J ust n oticeable d ifference ranges for e arly d ecay t ime grouped by receiver position Just Noticeable Difference Ranges for Early Decay Times by Receiver Female Talker Trumpet Song Balloon Pop Directional Speaker Omni directional Speaker Receiver 1 4 -18 0 -14 2 -21 0 0 -2 Receiver 2 2 -19 1 -17 1 -19 0 1 -4 Receiver 3 1 -19 0 -27 1 -17 0 0 -3 Figure 3 5 6 Balloon Pop Expanded and Perceptual Methods showing similar Just Noticeable Differences in E arly D ecay T ime The Perceptual WinMLS resulted in comparatively low JND values for the Balloon Pop, shown in Figure 3 5 7 This is most likely due to the high sound energy across the octave bands. As the frequency increases, the JND values increased as well. JND Values in the 500 Hertz octave band ranged from 0 2, 1 2 in the 1,000 Hertz octave band, and 2 3 in the 4,000 Hertz octave bands. 0 5 10 15 20 25 30 500 1000 4000 Just Noticeable Differences for EDT Octave Band Center Frequency in Hertz Balloon Pop JND for EDT Expanded Method Expanded Right R1 Expanded Left R1 Expanded Right R2 Expanded Left R2 Expanded Right R3 Expanded Left R3 0 5 10 15 20 25 30 500 1000 4000 Just Noticeable Differences for EDT Octave Band Center Frequency in Hertz Balloon Pop JND for EDT Perceptual Method Perceptual Right R1 Perceptual Left R1 Perceptual Right R2 Perceptual Left R2 Perceptual Right R3 Perceptual Left R3

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112 Figure 3 5 7 Balloon Pop Perceptual WinMLS method showing low JND values for E arly D ecay T ime The EDT metric resulted in the highest JND values of all the metrics analyzed in this study. The Female Talker 19. The Trumpet Song 27. The JND values ranged from 0 21 JND with the Balloo 80 For the Trumpet Song and the Balloon Pop the Expanded and Perceptual methods resulted other methods. For the two natural acoustic sources, the JND values increased as the receiver positions were farther from the source. However, with the Balloon Pop source, the opposite occurred, and the JND values increased as the receiver positions were clos er to the source. Clarity ( C 80 ) j ust n oticeable d ifferences The Trumpet Song has a slightly higher C 80 JND range than the Female Talker (0 8 as opposed to 0 Balloon Pop has the lowest JND range (from 0 Female Talker and Trumpet Song had the highest JND ranges in C 80 when analyzed using the Perceptual WinMLS method. 0 5 10 15 20 25 30 500 1000 4000 Just Noticeable Differences for EDT Octave Band Center Frequency in Hertz Balloon Pop JND for EDT Perceptual WinMLS Method Perceptual WinMLS Right R1 Perceptual WinMLS Left R1 Perceptual WinMLS Right R2 Perceptual WinMLS Left R2

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113 Table 3 5. C 80 j ust n oticeable d ifference ranges grouped by method Just Noticeable Difference Ranges for C 80 by Method Female Talker Trumpet Song Balloon Pop Directional Speaker Omni directional Speaker Traditional 0 4 0 5 0 5 0 0 Expanded 0 3 0 4 0 5 Perceptual 0 4 1 4 0 5 Perceptual WinMLS 1 6 1 8 0 4 The Female Talker had similar JND values when analyzed using the Expanded and Perceptual methods, as did the Trumpet Song which are shown in Figures 3 5 8 through 3 5 9 All 4 methods resulted in similar JND values when the Balloon Pop source was used. Figure 3 5 8 Graphs showing F emale T alker having similar JND values for C 80 across the octave bands for E xpanded and Perceptual methods 0 2 4 6 8 500 1000 4000 Just Noticeable Difference in C 80 Octave Band Center Frequency in Hertz Female Talker JND for C 80 Expanded Method Expanded Right R1 Expanded Left R1 Expanded Right R2 Expanded Left R2 Expanded Right R3 0 2 4 6 8 500 1000 4000 Just Noticeable Difference in C 80 Octave Band Center Frequency in Hertz Female Talker JND for C 80 Perceptual Method Perceptual Right R1 Perceptual Left R1 Perceptual Right R2 Perceptual Left R2 Perceptual Right R3 Perceptual Left R3

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114 Figure 3 5 9 Graphs sho wing T rumpet S ong having similar JND values for C 80 across the octave bands for Expanded and Perceptual methods Table 3 6. C 80 j ust n oticeable d ifference ranges grouped by receiver position Just Noticeable Difference Ranges for C 80 by Receiver Female Talker Trumpet Song Balloon Pop Directional Speaker Omni directional Speaker Receiver 1 0 5 0 5 2 3 0 0 Receiver 2 0 4 0 4 0 5 0 0 Receiver 3 0 6 0 8 0 3 0 0 Both the Female Talker and Trumpet Song JND values increased as the receiver position moved closer to the source. The Balloon Pop had similar JND values across the frequencies in all 3 receiver positions. The C 80 JND values for the F emale T alker tended to decrease as the receiver position was farther away from the source. The converse was true for the T rumpet S ong, as the C 80 JND tended to increase as the receiver position was farther from the source. Interestingly, the F emale T alker and 0 2 4 6 8 500 1000 4000 Just Noticeable Difference in C80 Octave Band Center Frequency in Hertz Trumpet Song JND for C80 Expanded Method Expanded Right R1 Expanded Left R1 Expanded Right R2 Expanded Left R2 Expanded Right R3 Expanded Left R3 0 2 4 6 8 500 1000 4000 Just Noticeable Difference in C80 Octave Band Center Frequency in Hertz Trumpet Song JND for C80 Perceptual Method Perceptual Right R1 Perceptual Left R1 Perceptual Right R2 Perceptual Left R2 Perceptual Right R3 Perceptual Left R3

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115 T rumpet S ong had the same range in C 80 er positions 1 and 2, as shown in Table 6. Discussion People gather in spaces for different purposes, whether it be to worship, learn, live, listen, or to be entertained. The transfer of information takes places via communication, be it verbal, visual, tactile, or other sensory perceptions. Aural communicat ion is the realm that acoustics deals with. When people communicate aurally with each other, the sounds they make are carried by direct and reflected paths throughout the room to reach the listener. The way in which these sounds interact with the room an d the paths they take to reach the listener are the primary concern of architectural acoustics. When a room creates desirable reflections that increase the direct and reflected sounds, has uniform decay and is free from acoustic defects such as echoes, th e sounds heard in the room will be judged by most to enhance the acoustics of the space. When the sounds from the source to the receiver are judged to not have the correct sonic characteristics, they are said to have acoustical defects. Acoustical measur ements are typically made in rooms as a tool to aid in designing the rooms to have preferred acoustical qualities for the specific sound sources and to avoid the acoustical defects. There are typically specific issues that are associated with the room tha t should be studied, i.e. : one cannot clearly hear speech in the room, or there are echoes present that muddy the music. Acousticians are brought in to determine how to remedy these issues. Kirkegaard and Gulsrud suggest that before any acoustical measur ements are made, the room be listened to, ideally using the sources that are known to produce the effects, so that the room attributes can be noted. They also suggest several other sources, including steady state noise and a metronome be

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116 used to reveal ti me domain issues. Only after the room has been listened to carefully and problematic receiver positions are identified are acoustical measurements taken. 9 This is not necessarily the typical method of diagnosing a room, especially in modern research. Ac ousticians take acoustical measurements in accordance with the applicable standards, such as ISO 3382, to perform diagnostics of the room. The measurements consist of omnidirectional sound sources that excite the room with a broadband signal at relativel y high levels. Measurements are derived from the backwards integration of the impulse response associated with each source. The problem therein lies in the fact that most sound sources found in a room are not omnidirectional, only excite a limited range of frequencies and are of varying sound levels. Conclusions There is the tendency for acoustical metrics to be given in the literature as whole room averages. There is typically one value for each acoustic metric for a given room. This has been shown t o be quite limited and that in reality, there are actually a range of values for each metric that vary with source and receiver type and position Kirkegaard reflection stru cture can be especially misleading if averaging over seating locations, since the most interesting and significant qualities of these parameters are often how 1 0 Recent research that has involved matrices of multiple receiver loc ations has shown that the acoustic metrics vary across receiver positions. 9 L. Kirkegaard and T. Gulsrud, Measure Acoustics Today 7 (2011): 7 8. 10

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117 This is in accordance with the idea that different seat positions will have different paths from source to receiver, with different reflection patterns at each seat, and therefore sounds will be heard differently in different seating positions. R esearchers have found that data vary across the room and acoustic parameters change based on the location of the source and receiver. It can be argued that this variance is not due to err or in the measurements but rather it is a function of the different paths from source to receiver, varying frequency content and levels, and directionality that causes these differences. While scientifically calibrated acoustical metrics provide reproduc ible results, the ways in which the scientifically calibrated sound sources excite a room are significantly different tha n the sounds that are typically heard in the room. The level, frequency content and directionality of the sound source affect the acou stic metrics derived from the measurements. This relates to the idea that people sitting in different seats in the rather due to the way that sounds with limited ba ndwidth, level and directionality interact with the room surfaces. This study suggests that because there is such large variation in acoustical metrics when using sound sources that are closer to those that would typically take place in a room, other meth ods for taking acoustical measurements should be developed that more closely relate the metrics to the sounds that are normally heard in the room. The Female Talker resulted in the highest JND of 0 to 22 in Reverberation Time, while the Trumpet Song had th 80 The Trumpet Song also had the highest JND values for EDT, ranging from 0 27. The acoustic metrics derived from the scientifically calibrated methods had JND less than 1 for the C 80 metric,

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11 8 between 0 and 4 JND in EDT an d between 0 and 2 JND for the RT. The directional JND of less than 1. It should be noted that for this study the 2,000 Hertz octave band was not analyzed due to there not being enough source signal from the Female Talker A n important example of how real sounds in rooms do not have the adequate level across the octave bands to derive acoustical metrics is t which was analyzed had limited signal in the octave bands. When using a broadband source, there is adequate sound level, especially in the middle frequencies to derive acoustical me trics. However, the absence of signal with this source should not be considered a defect in the source but rather a prime example of how real sounds have limited bandwidth and level, and yet these are the sounds that are actually heard in the rooms. A comparison of the broadband impulse response from each of the source signals is shown in Figure 3 60 Based on the impulse response graphs, one can see that the directional and omnidirectional loud speakers have similar (but not identical) impulse response s Each of the other sources has vastly different impulse responses, with different sound reflection patterns. It is the physical reality that these different sound sources, with different bandwidth, level transient response and directionality will soun d different at each receiver location and have different acoustical metrics associated with each condition

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119 Figure 3 60 Impulse response graphs of various sources used in study The data varies with source type and receiver position throughout the room. This variance is indicative of the different sources, the ways in which the data are processed and the receiver position in the room. The variances are not a resul t of error; the Talker and T rumpet Song have certain attributes that create these differences in acoustical metrics. The four methods of analyzing the recorded speech and music signals had similar results in many cases. The Traditional, Expanded and Per ceptual methods produced similar results, while the Perceptual WinMLS method had more varied results. Interestingly, the Expanded and Perceptual methods had extremely similar results, as the cursors for the r eflected sound and noise floor were ultimately placed in almost the same position. This may indicate that while it is generally accepted that the reflected sound should be calculated from 5dB from the direct sound and 10 dB above the ambient, our ears are able to hear more of the signal than what is included in the the other methods with the Balloon Pop as the sound source, produced different results fr om the natural acoustic sources This is most likely due to how the WinMLS software processes the data. It produces similar data with the sound source that is relatively Trumpet Song Female Talker Balloon Pop Directional MLS Omnidirectional MLS

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120 broadband, has high levels and a straight, steady decay. The other sources have limited bandwidth and level and uneven decay patterns, which may no t be analyzed properly by the analyzation software. To draw conclusions from the large amount of data that was collected, the left and right receivers in all 3 receiver positions were averaged to obtain single numbers per octave band for each source and method. From the RT EDT comparison, the Perceptual WinMLS data not only had data that ranged from 0 to 0.2 seconds, which is comparable to previous studies by Bradley, but also had values that were within 0.2 seconds from the 0 value, which means they h ad almost the same values as the average RT EDT values derived using the MLS source. Figure 3 6 1 Average RT EDT values for Female Talker source -0.5 0 0.5 1 1.5 2 2.5 500 1000 4000 Difference in RT EDT in Seconds Octave Band Center Frequency in Hertz Average RT EDT: Female Talker Average Traditional Method Average Expanded Method Average Perceptual Method Average Perceptual WinMLS Method

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121 Figure 3 6 2 Average RT EDT values for Trumpet Song source Figure 3 6 3 Average RT EDT values for Trumpet Song source -0.5 0 0.5 1 1.5 2 2.5 500 1000 4000 Difference in RT EDT in Seconds Octave Band Center Frequency in Hertz Average RT EDT: Trumpet Song Average Traditional Method Average Expanded Method Average Perceptual Method Average Perceptual WinMLS Method -0.5 0 0.5 1 1.5 2 2.5 500 1000 4000 Difference in RT EDT in Seconds Octave Band Center Frequency in Hertz Average RT EDT: Balloon Pop Average Traditional Method Average Expanded Method Average Perceptual Method Average Perceptual WinMLS Method

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122 Reverberation time is typically considered a consistent metric when measured throughout a room Wallace Sabine performed experiments in which he varied the source and receiver locations while measuring RT. He found little variance between the positions. However, performing measurements using the natural acoustic sources to was found to have extremely high J ust Noticeable Differences (up to 22 3382. The Expanded and Perceptual Method s were within 0.01 and 0.06 seconds in the 1,000 and 4,000 Hertz octave bands for all 3 sources The Traditional, Expanded and Perceptual Methods were within .02 to 0.12 seconds of each other in all octave bands f or Balloon Pop source shown in Figure 3 66 that were very close to the average MLS data, ranging from just 0.03 to 0.18 seconds from the average Figure 3 6 4 Average Normalized Reverberation Time for Fem ale Talker source -2 -1.5 -1 -0.5 0 0.5 500 1000 4000 Normalized Reverberation Time in Seconds Octave Band Center Frequency in Hertz Average Normalized Reverberation Time: Female Talker Average Traditional Method Average Expanded Method Average Perceptual Method Average Perceptual WinMLS

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123 Figure 3 6 5 Average Normalized Reverberation Time for Trumpet Song source Figure 3 6 6 Average Normalized Reverberation Time for Balloon Pop source The EDT metrics produced the most variation between methods with up to 27 0.03 to 0.38 seconds from each other using the Traditional, Perceptual and Perceptual -2 -1.5 -1 -0.5 0 0.5 500 1000 4000 Normalized Reverberation Time in Seconds Octave Band Center Frequency in Hertz Average Normalized Reverberation Time: Trumpet Song Average Traditional Method Average Expanded Method Average Perceptual Method Average Perceptual Method -2 -1.5 -1 -0.5 0 0.5 500 1000 4000 Normalized Reverberation Time in Seconds Octave Band Center Frequency in Hertz Average Normalized Reverberation Time: Balloon Pop Average Traditional Method Average Expanded Method Average Perceptual Method Average Perceptual WinMLS Method

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124 WinMLS Methods shown in Figure 3 67 The Trumpet Song resulted in similar Expand ed and Perceptual methods, varying from 0.08 to .16 seconds from each other shown in Figure 6 68 The Perceptual WinMLS EDT values were within .03 to 0.1 seconds of the average MLS data for the Balloon Pop source, shown in Figure 3 69 Figure 3 6 7 Av erage Normalized Early Decay Time for Female Talker source Figure 3 6 8 Average Normalized Early Decay Time for Trumpet Song source -2.5 -2 -1.5 -1 -0.5 0 0.5 500 1000 4000 Normalized EDT in Seconds Octave Band Center Frequency in Hertz Average Normalized Early Decay Time: Female Talker Average Traditional Method Average Expanded Method Average Perceptual Method Average Perceptual WinMLS Method -2.5 -2 -1.5 -1 -0.5 0 0.5 500 1000 4000 Normalized EDT in Seconds Octave Band Center Frequency in Hertz Average Normalized Early Decay Time: Trumpet Song Average Traditional Method Average Expanded Method Average Perceptual Method Average Perceptual WinMLS Method

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125 Figure 3 6 9 Average Normalized Early Decay Time for Balloon Pop source The C 80 values had more clearly defined simila rities between methods than the EDT. The C 80 8. The Expanded and Perceptual Methods resulted in similar C 80 values, differing between 0 and 0.6 dB for the Female Talker source shown in Figure 3 70 All 4 methods had similar values for the Trumpet Song, differing by 0.17 to 1.22 dB. The Traditional, Expanded and Perceptual methods when analyzing the Balloon Pop shown in Figure 3 72 resulted in almost exactly the same values, differing by just 0 to 0.06 dB. Figure 3 70 Average Normalized Clarity (C 80 ) for Female Talker source -2.5 -2 -1.5 -1 -0.5 0 0.5 500 1000 4000 Normalized EDT in Seconds Octave Band Center Frequency in Hertz Average Normalized Early Decay Time: Balloon Pop Average Traditional Method Average Expanded Method Average Perceptual Method Average Perceptual WinMLS Method -4 -3 -2 -1 0 1 2 3 500 1000 4000 Normalized C 80 in decibels Octave Band Center Frequency in Hertz Average Normalized C 80 : Female Talker Average Traditional Method Average Expanded Method Average Perceptual Method Average Perceptual WinMLS Method

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126 Figure 3 7 1 Average Normalized Clarity (C 80 ) for Trumpet Song source Figure 3 7 2 Average Normalized Clarity (C 80 ) for Balloon Pop source As Figure 3 73 shows, much of the data derived from the natural acoustic sources was below that of the average MLS data. There are only 4 data points that are above the scientifically calibrated sources. These data are from natural acoustic sources analyzed during the Pilot Study, before consistent methods for analyzing natural acoustic sources were adopted -4 -3 -2 -1 0 1 2 3 500 1000 4000 Normalized C 80 in decibels Octave Band Center Frequency in Hertz Average Normalized C 80 : Trumpet Song Average Traditional Method Average Expanded Method Average Perceptual Method Average Perceptual WinMLS Method -5 -4 -3 -2 -1 0 1 2 3 500 1000 4000 Normalized C 80 in decibels Octave Band Center Frequency in Hertz Average Normalized C 80 : Balloon Pop Average Traditional Method Average Expanded Method Average Perceptual Method Average Perceptual WinMLS Method

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127 Figure 3 sources 0.6 1 1.4 1.8 2.2 2.6 3 500 1000 4000 Reverberation Time in Seconds Octave Band Center Frequency in Hertz Pilot Study: Dir corner sine sweep Pilot Study: Dir Front Sine Sweep Pilot Study: Mult Sine Sweep Dir Corner Pilot Study: Mult Sine Sweep Dir Front Pilot Study: Dir Front MLS Pilot Study: Dir Corner MLS Pilot Study: Balloon Pop MLS Pilot Study: Balloon POP AT Pilot Study: Female Talker Pilot Study: Piano Middle C Note Pilot Study: Piano Middle C Chord Pilot Study: Piano Song Pilot Study: Trumpet Song Study 1: Dir Front MLS Study 1: Dodec Front MLS Study 2: Traditional Method: Balloon Pop Study 2: Traditional Method: Female Talker Study 2: Traditional Method: Trumpet Song Study 2: Expanded Method: Balloon Pop Study 2: Expanded Method: Female Talker Study 2: Expanded Method: Trumpet Song Study 2: Perceptual Method: Balloon Pop Study 2: Perceptual Method: Female Talker Study 2: Perceptual Method: Trumpet Song Study 2: Perceptual WinMLS Method: Balloon Pop Study 2: Perceptual WinMLS Method: Female Talker Natural Acoustic Sources Scientifically Calibrated Sources Data from natural acoustic sources from Pilot Study before consistent methods for analyzing natural acoustic sources were developed

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128 Data from the same sources were reanalyzed using methods 1 4 and yielded results that were lower than data derived from the scientifically calibrated sources. On average, the natural acoustic sources had Reverberation Times that were between 0.28 and 0.44 seconds shorter than the scientifically calibrated sources because the natural acoustic sources had lower sound levels, limited bandwidth and did not fully excite the reverberant field of the room. For the Reverberation Time metric, 86% of the natural acoustic data was below the average MLS data. Of the 30 data points that were above the average MLS, 60% were from the Trumpet Song. The EDT metric also resulted in 86% of the data derived from the natural acoustic sources falling bel ow the average MLS data. This is most likely due to the Trumpet Song having high sound levels in the 500, 1,000 and 4,000 Hertz octave bands that were analyzed. Again, the Trumpet Song accounted for most of the data points above the average MLS, with 5 8% above the average. The higher than average MLS values for RT and EDT are most likely due to the Trumpet Song having high sound levels in the 500, 1,000 and 4,000 Hertz octave bands that were analyzed. The values for the Clarity Index derived from the natural acoustic sources were generally below the average MLS values, with 73% of the natural acoustic data falling below the average MLS data. The Female Talker had the most data above the average MLS values, with 43% of the data above the average. The Female Talker had lower RT values, and as such, makes sense that it has higher Clarity values. The Clarity Index is dependent on the early and late reverberation. If there is less late reverberation, the C 80 values will be higher than if there were larg e amounts of late reverberation.

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129 Future Studies While this study does not intend to prove a new methodology for taking acoustic measurements, it intends to highlight the degree of differentiation between certain acoustic metrics derived from more reali stic sound sources to provide an impetus for further study. For all 4 methods of analysis for alternative sound sources, scientifically calibrated method. The R eve rberation T ime value s for all 4 methods were R everberation T ime obtained in general accordance with ISO 3382. The large differences suggest that acoustical conditions vary in the room based on source type and listener l ocation. It is suggested that similar studies be conducted in which more sources are used; including different words and sentences so that metrics may be derived from different words and syllables. Other instruments should also be used, which have diffe rent directivity pattern s, bandwidth, content and level Other larger rooms should be used, that would possibly have larger differences in the acoustical metrics derived using ISO 3382. It would be beneficial to compare a room whose metrics are more similar to a larger room that has larger variances from testing in accordance with ISO 3382. Using more receiver positions would also be helpful, so a grid could be made of the acoustic metrics. Testing of more than one room would also be beneficial, so as to compare the results across multiple room conditions. Subjective listening tests may also be conducted in the receiver positions to determine if the metrics derived from the natural acoustic source measurement methods relate n of the natural acoustic source at that position.

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130 APPENDIX A IMPULSE RESPONSE PRINTOUTS FOR WIN MLS SOURCES Figure A 1. MLS Directional Front: Receiver 3_1 Figure A 2. MLS Directional Front: Receiver 3_2 Figure A 3. MLS Directional Front: Receiver 3_3 Figure A 4. MLS Directional Corner: Receiver 3_1

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131 Figure A 5. MLS Directional Corner: Receiver 3_2 Figure A 6. MLS Directional Corner: Receiver 3_3 Figure A 7. Sine Sweep Directional Front: Receiver 3_1 Figure A 8. Sin e Sweep Directional Front: Receiver 3_2

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132 Figure A 9. Sine Sweep Directional Front: Receiver 3_3 Figure A 10. Sine Sweep Directional Corner: Receiver 3_1 Figure A 11. Sine Sweep Directional Corner: Receiver 3_2 Figure A 12. Sine Sweep Directional Corner: Receiver 3_3

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133 Figure A 13. Multiple Sine Sweep Directional Front: Receiver 3_1 Figure A 14. Multiple Sine Sweep Directional Front: Receiver 3_2 Figure A 15. Multiple Sine Sweep Directional Front: Receiver 3_3 Figure A 1 6. Multiple Sine Sweep Directional Corner: Receiver 3_1

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134 Figure A 17. Multiple Sine Sweep Directional Corner: Receiver 3_2 Figure A 18. Multiple Sine Sweep Directional Corner: Receiver 3_3 DECAY CURVES OF ANECHOIC, PIANO AND BALLOON SIGNALS IN THE 500 and 1,000 HERTZ OCTAVE BANDS ANALYZED USING ACOUSTIC TOOLS Figure A 19. Piano Middle C Note: 500 Hertz

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135 Figure A 20. Piano Middle C Note: 1,000 Hertz Figure A 21. Piano Middle C Chord: 500 Hertz

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136 Figure A 22. Piano Middle C Chord: 1,000 Hertz Figure A 23. Piano Song Stop Chord: 500 Hertz

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137 Figure A 24. Piano Song Stop Chord: 1,000 Hertz Figure A 25. Anechoic Trumpet Music: 500 Hertz

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138 Figure A 26. Anechoic Trumpet Music: 1,000 Hertz Figure A 27. Anechoic Female Talker: 500 Hertz

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139 Figure A 28. Anechoic Female Talker: 1,000 Hertz

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140 APPENDIX B OMNIDIRECTIONAL AND DIRECTIONAL LOUDSPEAKER COMPARISON Figure B 1. MLS Directional Front: Receiver 1_1 Figure B 2. MLS Directional Front: Receiver 1_2 Figure B 3. MLS Directional Front: Receiver 1_3 Figure B 4. MLS Directional Front: Receiver 2_1

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141 Figure B 5. MLS Directional Front: Receiver 2_2 Figure B 6. MLS Directional Front: Receiver 2_3 Figure B 7. MLS Directional Front: Receiver 3_1 Figure B 8. MLS Directional Front: Receiver 3_2

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142 Figure B 9. MLS Directional Front: Receiver 3_3 Figure B 10. MLS Omnidirectional Front: Receiver 1_1 Figure B 11. MLS Omnidirectional Front: Receiver 1_2 Figure B 12. MLS Omnidirectional Front: Receiver 1_3

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143 Figure B 13. MLS Omnidirectional Front: Receiver 1_4 Figure B 14. MLS Omnidirectional Front: Receiver 1_5 Figure B 15. MLS Omnidirectional Front: Receiver 2_1 MLS Figure B 16. MLS Omnidirectional Fr ont: Receiver 2_2

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144 Figure B 17. Omnidirectional Front: Receiver 2_3 Figure B 18. MLS Omnidirectional Front: Receiver 2_4 Figure B 19. MLS Omnidirectional Front: Receiver 2_5 Figure B 20. MLS Omnidirectional Front: Receiver 3_1

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145 Figure B 21. MLS Omnidirectional Front: Receiver 3_2 Figure B 22. MLS Omnidirectional Front: Receiver 3_3 Figure B 23. MLS Omnidirectional Front: Receiver 3_4 Figure B 24. MLS Omnidirectional Front: Receiver 3_5

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146 LIST OF REFERENCES The Journal of the Acoustical Society of America 126 (2009): 2288. Akama, T., H. Suzuki, and A. Omoto. Applied Acoustics 71 (2010): 564 577. al, 2004. Baughman Center [Web site] (2010); available from http://performingarts.ufl.edu/venues/baughman center/ ; Internet; accessed 10 August 2010 Beranek, L. L. Concert and Opera Hal ls: How They Sound Woodbury, NY: Published for the Acoustical Society of America through the American Institute of Physics, 1996. of Concert Halls with Suspended Panel Ar Acustica 15 (1965): 307 316. Blesser, B., and L. Salter. Spaces Speak, Are You Listening?: Experiencing Aural Architecture. Cambridge, Mass: MIT Press, 2007. Computer Simulat The Journal of the Acoustical Society of America 105 (1999): 753 763, The Journal of the Acoustical Society of America 89 (1991): 1176 1192. Bradley, J. S., R. Reich, and S. G. Norcros Applied Acoustics 58 (1999): 99 108. Principles and Applications of Room Acoustics. London: Applied Science,1982. Egan, M. D. Architectural Acoustics New York: McGraw Hi ll,1988. Measurement of the reverberation time of rooms with Standardization, Geneva, Switzerland. up Process of Sound Pulses i n a Room and its Relation to Proceedings of the 3rd ICA, Stuttgart, 1959, Vol. II Amsterdam: Elsevier, 1961: 922 925.

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147 The Journal of the Ac oustical Society of America 47 (1970): 408 412. Acoustics Today 7 (2011): 7 13. Kleiner, M., D. L. Klepper, and R. R. Torres. Worship Space Acoustics. Ft. Lauderdale: J. Ross Publishing, 2010. Balcony Acoustics with Real 2006. Echoes, Their Primary Sounds, and Their Contributions to the Intelligibility of Acustica 8 (1958): 1 10. nce of Center Time and Clarity Index in Large Reverberant The Journal of the Acoustical Society of America 123 (2008): 133 138. Nor276 Dodecahedron Loudspeaker [website] available from http://cn.jblpro.com/catalog/support/getfile.aspx?doctype=3&docid=239 ; Internet; accessed 12 July 2012. Norsonic 213 and 223 Dodecahedron Speaker Specifications [Web site] available from http://www.gracey.com/descriptions/nor_213 d1.htm ; Internet; accessed 12 July 2012. Olson, H. F. Music, Physics and Engineering (New York: Dover Publications, Inc.,1967) The Journal of the Acoustical Society of America 129 (2011): 27 33. c Parameters as a Function of Source Location Acustica 32 (1975): 126 137. Sabine, W. C. Collected Papers on Acoustics. New York: Dover Publications, 1964. The Journal of the Acoustical Society of America 37 (1965): 409 412.

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148 Schafer, R. M. The Soundscape: Our Sonic Environment and the Tuning of the World Ro chester, VT: Destiny Books, 1994. presented at Designing Soundscape for Sustainable Urban Development Conference, Stockholm, Sweden, September 30 October 1, 2010. Sklevi Proceedings of the 20th International Conference on Acoustics. Sydney, Australia. August 23 27, 2010: 1 6. d The Journal of the Acoustical Society of America 131 (2012): 1206 1220. Auditorium Acoustics ed. by Robin MacKenzie, 21 43. New York: John Wiley and Sons, 1974.

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149 BIOGRAPHICAL SKETCH Keely Siebein has been involved in architectural acoustics from a young age, being first exposed to the field by her father, Gary Siebein. She wor ked in acoustical consulting firm from the time she was 15 years old, researching classroom acoustics and performing technical acoustical measurements. She continued to work with her father throughout high school and college. She majored in Theater at the University of Florida for her undergraduate degree, minored in French, and graduated with Honors in 2007. She started the Master of Science in Architectural Studies with an emphasis in Architectural Acoustics in 2009. Throughout her Master also worked as a Consultant at Siebein Associates, Inc. She has worked on over 65 architectural and environmental acoustical projects professionally She is currently working on books on the Natural Soundscape, the Soundscape of Ichetuckne e, and Classroom Acoustics.