Citation
Age-related differences in articulatory physiology among adult females

Material Information

Title:
Age-related differences in articulatory physiology among adult females
Creator:
Morris, Richard Jack, 1950- ( Dissertant )
Brown, Samuel W. ( Thesis advisor )
Hollien, Harry F. ( Reviewer )
Yang, Mark C. ( Reviewer )
Hicks, Douglas, M. ( Reviewer )
Webb, Lynne M. ( Reviewer )
Place of Publication:
Gainesville, Fla.
Publisher:
University of Florida
Publication Date:
Copyright Date:
1986
Language:
English
Physical Description:
vii, 136 leaves : ill. ; 28 cm.

Subjects

Subjects / Keywords:
Age groups ( jstor )
Air pressure ( jstor )
Consonants ( jstor )
Older adults ( jstor )
Phonemes ( jstor )
Pressure ( jstor )
Spoken communication ( jstor )
Stop consonants ( jstor )
Syllables ( jstor )
Vowels ( jstor )
Aging ( lcsh )
Articulation disorders ( lcsh )
Dissertations, academic -- Speech -- UF
Speech -- Physiological aspects ( lcsh )
Speech thesis Ph. D
Genre:
bibliography ( marcgt )
non-fiction ( marcgt )

Notes

Abstract:
The purpose of this study was to examine differences between the speech of women in two age groups, 20-30 years old and over 75 years old. Age-related differences in peak intraoral air pressure (PIO), consonant duration (CD), vowel duration (VD), voice onset time (VOT), and vocal intensity were studied. The intensity task consisted of three repetitions of sustained /Q / at three loudness levels. For the other speech tasks, consonant-vowel (CV) , vowel-consonant- vowel (VCV) , and vowel-consonant (VC) syllables were embedded in the carrier phrase "Speak again." The consonants were /p, t, b, d, s, and z/ combined with /a/. Short samples from the syllable task were played to listeners who estimated the ages of the speakers. The listeners consistently estimated ages that closely approximated the chronological age of the speakers, r=.88. Peak PIO magnitudes did not differ significantly between the young and non-denture wearing older speakers. The denture wearing older speakers exhibited higher peak PIO values for the voiceless consonants. CD values were longer among the older speakers for the test consonants except for /t/. The older speakers exhibited significant increases in VD. The older group also exhibited consistently shorter VOT values than the younger speakers, but not enough to change normal perceptual identification. For the intensity tasks the older speakers exhibited narrower intensity ranges, the range being restricted at both the minimum and maximum effort levels. All of the dependent variables exhibited greater variability among the older speakers. The conversational intensity and PIO results indicate that age-related physiologic differences do not significantly affect the pressure levels associated with normal speech. Similarly, the VOT data indicated that this parameter was not meaningfully affected by the aging process. Increased consonant and vowel durations may be related to the percept of a slower speech rate for older speakers, while the greater variability for all of the dependent variables for the older speakers may be related to the percept of less precise articulation among geriatric speakers
Thesis:
Thesis (Ph. D.)--University of Florida, 1986.
Bibliography:
Bibliography: leaves 115-126.
General Note:
Typescript.
General Note:
Vita.
Statement of Responsibility:
by Richard Jack Morris.

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University of Florida
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University of Florida
Rights Management:
Copyright [name of dissertation author]. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Resource Identifier:
000893024 ( alephbibnum )
AEK1535 ( notis )
015279688 ( oclc )

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AGE-RELATED DIFFERENCES IN ARTICULATORY
PHYSIOLOGY AMONG ADULT FEMALES











By

RICHARD JACK MORRIS


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN
PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE DEGREE OF DOCTOR OF PHILOSOPHY




UNIVERSITY OF FLORIDA


1986












ACKNOWLEDGEMENTS


There are so many who have helped make this project

possible that it is difficult to enumerate the responsible

parties. First, I would like to acknowledge the guidance

and support that I have received from the members of my

supervisory committee. Dr. Douglas Hicks, Dr. Harry

Hollien, Dr. Lynne Webb, and Dr. Mark Yang have all offered

their time and knowledge. I also wish to offer my thanks

and appreciation to my mentor and chairperson, Dr. W. S.

Brown, Jr. He helped me by prodding me onward, joking with

me, and keeping his door open for me when I have needed

help. Even when I have been at my clumsiest, I have felt I

was respected.

My fellow students in IASCP and the Speech department

have been a source of solace and ideas. People who deserve

individual mention are Ruth Huntley, Donald Goldberg, Karen

Massey, Janet Harrison, Brian Klepper, Tom Sawallis, Ernie

Hepler, and Lynne Harshman. To this group I must add Juan

Talavera-Martin, a man who helped me immensely in many ways.

I also need to acknowledge my religious community, the

people who share my foundation: the special corner of

Judaism, B'nai Or, and its members Dennis Shuman, Renee

Hoffinger, Shelly Isenberg, Bahira Sugarman, Rick Chess,

Michael Koszegi, Gayle Mann, Elsa Kula, and John Simpson;

ii








also, the congregation at B'nai Israel, particularly Rabbi

Allan Lehmann and Howard Rothman.

The support and encouragement that I have received from

my family, even though we are separated by miles, have been a

constant buoy. My brother, Fred Morris, my sister, Linda

Thornton, and my parents Jack and Ruth Morris have given me

more than I can express.

The daily sharing of the trials and tribulations of

this project and unconditional, unselfish love provided by

my wife, Jamie Wulkan, is truly the source of energy from

which this project came. May I live long enough to share as

much with her as she has shared with me.

At the very last, as at the very first, this and all

things are a gift from the holy one, blessed be the name.

May we see the blessing in all that we do.















TABLE OF CONTENTS


Page


ACKNOWLEDGMENTS . . . . . . . . . .


ABSTRACT . . . . . . . . . .


CHAPTERS

I INTRODUCTION . . . . . . . . .

II LITERATURE REVIEW . . . . . . .

Increased Number of Older People . . . .
Age-Related Physiologic Differences . . .
Measurement of Speech Timing, Intraoral Air
Pressure and Speech Intensity . . . .
Purpose . . . . . . . . . .
Hypotheses . . . . . . . . . .

III METHODS . . . . . . . .. ..

Subjects . . . . . . . . . .
Equipment . . . . . . . . .
Procedures . . . . . . . . . .
Analyses . . . . . . . . . .

IV RESULTS . . . . . . . . . ..

Introduction . . . . . . . . .
Research Findings . . . . . . .
Summary of Results . . . . . . . .

V DISCUSSION . . . . . . . . . .

Introduction . . . . . . . . .


Speech Production Similarities Between
the Two Groups . . . .
Speech Production Differences Between
the Two Groups . . . .
Implications for Future Research . .
Conclusion . . . . . . .


REFERENCES . . . . . . . . . . .


vi


97


. . 99


f I I f









APPENDICES

A HEALTH STATUS QUESTIONNAIRE. . . . . ... 127

B DIAGRAM OF TIMING AND PRESSURE RECORDING
EQUIPMENT . . . . . . . . 129

C RESPONSE FORM FOR PERCEPTUAL TASK. . . .. .131

BIOGRAPHICAL SKETCH . . . . . ... . . .. 135














Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy


AGE-RELATED DIFFERENCES IN THE ARTICULATORY
PHYSIOLOGY OF ADULT WOMEN

by

Richard Jack Morris

August 1986

Chairman: W. Samuel Brown, Jr.
Major Department: Speech

The purpose of this study was to examine differences

between the speech of women in two age groups, 20-30 years

old and over 75 years old. Age-related differences in peak

intraoral air pressure (PIO), consonant duration (CD), vowel

duration (VD), voice onset time (VOT), and vocal intensity

were studied. The intensity task consisted of three

repetitions of sustained /a/ at three loudness levels. For

the other speech tasks, consonant-vowel (CV), vowel-

consonant-vowel (VCV), and vowel-consonant (VC) syllables

were embedded in the carrier phrase "Speak __ again."

The consonants were /p, t, b, d, s, and z/ combined with

/a/. Short samples from the syllable task were played to

listeners who estimated the ages of the speakers. The

listeners consistently estimated ages that closely

approximated the chronological age of the speakers, r=.88.

vi









Peak PIO magnitudes did not differ significantly

between the young and non-denture wearing older speakers.

The denture wearing older speakers exhibited higher peak

PIO values for the voiceless consonants. CD values were

longer among the older speakers for the test consonants

except for /t/. The older speakers exhibited significant

increases in VD. The older group also exhibited consis-

tently shorter VOT values than the younger speakers, but not

enough to change normal perceptual identification. For the

intensity tasks the older speakers exhibited narrower

intensity ranges, the range being restricted at both the

minimum and maximum effort levels. All of the dependent

variables exhibited greater variability among the older

speakers.

The conversational intensity and PIO results indicate

that age-related physiologic differences do not signifi-

cantly affect the pressure levels associated with normal

speech. Similarly, the VOT data indicated that this

parameter was not meaningfully affected by the aging

process. Increased consonant and vowel durations may be

related to the percept of a slower speech rate for older

speakers, while the greater variability for all of the

dependent variables for the older speakers may be related to

the percept of less precise articulation among geriatric

speakers.














CHAPTER I
INTRODUCTION

One of the outstanding demographic phenomena of the

twentieth century is the aging of populations in developed

nations. Extended life expectancy and reduced birth rate

have resulted in those over age 65 being an increasing

proportion of the population. As the population has aged,

increasing numbers of health related professionals have

investigated the sociologic, psychologic, anatomic, and

physiologic ramifications of a larger aged population.

The aging process includes organismic alterations to

neurotransmission, muscle strength, and mucosal elasticity.

These alterations of the entire human organism influence

speech production. The speech produced is so altered that

people can determine the age of speakers from taped speech

samples (Hartman, 1979; Hartman & Danhauer, 1976; Ptacek &

Sander, 1966; E. Ryan & Capadano, 1978; Shipp & Hoilien,

1969). The relationship between perceived age differences

among speakers and the physiologic changes in the speech

production mechanism has not been investigated. Addi-

tionally, few extant studies have examined the effect of

known age-related physiologic changes on speech production.

The physiologic changes within the speech production

mechanism that occur with aging may alter certain measurable










parameters of speech. Research indicates that one para-

meter, speech timing, is affected by aging (Mysak, 1959;

Mysak & Hanley, 1959; W. Ryan, 1972). Two other parameters

that may be affected by aging include the ability to gener-

ate typical values of intraoral air pressure and vocal

intensity. These three parameters are among the most

important factors in creating and maintaining intelligible

speech production (Lisker & Abramson, 1964; Muller & Brown,

1980; Peterson & Lehiste, 1960). Age-based changes within

any of these parameters may implicate specific structural

changes in the speech production mechanism.

Previous studies have found that geriatric subjects

speak more slowly than young adult subjects (Mysak, 1959;

Mysak & Hanley, 1959; W. Ryan, 1972). W. Ryan (1972) found

that when pauses were removed from speakers' discourse, the

older subjects still exhibited a slower speaking rate than

younger subjects. This indicates that some segment of the

speech signal is slower among older speakers. The slowed

speech rate may be due to differences in consonant closure

duration. This could imply that older speakers are slower

in initiating and completing consonants, or that more time

is needed to impound adequate intraoral air pressure. A

second possibility is that the slowed speech rate is due to

a difference in vowel duration. This could imply that the

smooth transitions between the consonants are sustained

longer to be certain that they are perceived correctly or










that the oral motor system is slower in completing

transitions.

A final aspect of speech timing that may be involved in

perceived age differences is voice onset time. Previous

studies of aging and voice onset time have yielded disparate

results that include reduced voice onset times among older

subjects (Benjamin, 1982), no age differences in voice onset

time (Neiman, Klich, & Shuey, 1983), and increased varia-

bility in voice onset times among older speakers (Sweeting

and Baken, 1982) finding of increased variability among

older speakers. Further investigation of voice onset time

may clarify how aging influences the timing interaction

between articulation and phonation.

In addition to speech timing, intraoral air pressure

and sound pressure level for speech may be altered by aging.

Intraoral pressure is an important aspect of stop and

fricative consonants, as sound pressure level is with

vowels. Both of these pressures depend upon the air flow

from the respiratory system.

While older subjects exhibit reduced vital capacity

(Alexander & Kountz, 1932; Pierce & Ebert, 1965; Ptacek,

Sander, Maloney, & Jackson, 1966; Pump, 1971), the effect of

this reduction on speech has not been clearly documented.

Ptacek et al. (1966) stated that the reduction of vital

capacity is related to reduced maximum levels of intraoral

air pressure in older subjects. However, this relationship

has not been tested for conversational utterances.










Age differences in vocal intensity have been examined

at both maximum and comfortable effort levels. Ptacek et

al. (1966) found that older subjects exhibited lower

intensity than younger subjects at maximum effort levels,

while W. Ryan (1972) reported that older subjects' speech

intensity was greater than that of younger subjects at

comfortable effort levels. It could be hypothesized that if

the vocal intensity of older subjects is reduced at all

effort levels, this would indicate that reduced vital

capacity affects vocal intensity (Ptacek et al., 1966).

However, if the older people show increased vocal intensity,

then other physiologic changes, such as reduced oral

proprioception would be implied. An investigation of vocal

intensity at maximum, minimum, and comfortable levels should

indicate which aging changes are salient to vocal intensity.

This research project investigated the age-related

physiologic changes within the speech production mechanism

as demonstrated by speech timing, intraoral air pressure,

and vocal intensity. Specifically, it involved comparing

two age groups along the parameters phoneme duration, voice

onset time, intraoral pressure, and sound pressure level.














CHAPTER II
LITERATURE REVIEW

Increased Number of Older People

Since the turn of the century, an increasingly larger

proportion of the population of the United States is living

past age 65. Hayflick (1981) stated that in the developed

countries, the reduction of mortality from early childhood

diseases has resulted in the survival of a greater propor-

tion of the population to adulthood and old age. In 1900

one of every six infants died in the first 12 months of

life, by 1982 this was reduced to one of every 88 (Yin &

Shine, 1985). At the other end of the life span, reduction

of diseases prevalent among older people has added only two

to three years to life expectancy (Hayflick, 1981). In

other words, the decreased rate of premature deaths has been

the major factor in the increase of life expectancy at birth

from 47 years in 1900 to 75 years in 1982 (Yin & Shine,

1985). The trend of an increasing proportion of older

people in the population is predicted to continue into the

twenty-first century.

The increasing number of older people within the popu-

lation has prompted many health related professionals to

investigate the effect that age-related sociologic, psycho-

logic, acoustic, anatomic, and physiologic changes have on

normal functioning. These changes may create new problems,

5










exacerbate existing problems, and affect appropriate

treatment of problems. Practitioners in the health related

professions must differentiate between normal aging changes

and abnormal changes in order to correctly diagnose and

treat problems. Professionals in communication have begun

to probe the effects age-related physiologic changes may

have on communication skills.

Age-Related Physiologic Differences

Organismic Differences

Humans over 70 years old exhibit reduced physiologic

ability when compared to younger populations. Physiologic

differences include reduced speed of neurologic transmission

(LaFratta & Canestrari, 1966; Norris, Shock, & Wagman,

1953), reduced maximum muscle strength (Welford, 1977),

reduced speed of muscle action (Welford, 1977), and reduced

elasticity of extracellular connective tissue (Hall, 1976).

These aging changes occur at differing rates in various body

systems, with greater reductions in systems involving a

number of connections between nerves and other nerves or

muscles (Weg, 1975).

Speech Production Mechanism Differences

Review articles by Kahane (1981) and Meyerson (1976)

have described how the age-related organismic physiologic

differences alter each of the speech production systems:

respiration, phonation, and articulation. The present

discussion will focus on the aging differences found in these










three speech systems as they may relate to speech timing,

magnitudes of intraoral air pressure, and speech intensity.

Respiratory system

The lower respiratory system of older people exhibits

decrements in its component parts (Kahane, 1981; Meyerson,

1976). It consists of the rib cage and connected vertebrae,

the diaphragm and other thoracic musculature, the lungs, the

bronchial tubes, and the trachea below the vocal folds

(Zemlin, 1968). Studies of aging differences within the

respiratory system have tended to focus on either the

thoracic wall or the tissues within the lungs.

Age-related changes to the thoracic wall. The

vertebral column and rib cage exhibit structural changes

with aging. The vertebral column of older people undergoes

kyphosis, or a change in curvature (Alexander & Kountz,

1932). The range of motion of ribs connected to these

vertebrae is restricted by the kyphosis as well as decalci-

fication of the ribs (Alexander & Kountz, 1932; Dhar,

Shastri, & Lenora, 1976). Bates and Christie (1955) and

Dhar et al. (1976) reported that their older subjects

exhibited a "barrel chest" configuration of the costal

cartilages, leaving the rib cage in an elevated position.

An elevated resting position of the rib cage reduces the

volume of air which may be forced out of the lungs, thereby

reducing vital capacity (Alexander & Kountz, 1932; Bates &

Christie, 1955).










Similarly, age-related weakening of the thoracic

musculature may reduce mobility of the thoracic wall.

Several authors include thoracic muscle weakening as a

factor in the reduced vital capacity of older subjects in

comparison to younger subjects (Dhar et al., 1976; Kahane,

1981; Meyerson, 1976; Thurlbeck, 1979); however, a paucity

of data exists to quantify the role of the weakening of the

thoracic wall musculature in reduced vital capacity among

older subjects. Researchers have cited previous studies

based on clinical impressions or their own clinical

impressions in reporting the weakening of the thoracic wall

musculature. Regardless of the status of the thoracic wall

musculature, reduction of mobility of the bones of the

thoracic wall is a significant factor in the reduction in

vital capacity.

Age-related changes within the lung. In addition to

the changes in the thoracic wall, structural changes within

the aged lung operate to reduce vital capacity. A breakdown

of the structure of the elastic fibers occurs within the

lungs, with a concomitant increase in the mass of elastic

tissue in the pleura and septa of the lungs (Pierce & Ebert,

1965; Pump, 1971; Thurlbeck, 1979). These changes reduce

the vital capacity of older people by reducing the elastic

recoil of the lung (Pierce & Ebert, 1965; Pump, 1971; Shock,

1962; Thurlbeck, 1979; Turner, Mead, & Wohl, 1968). The

diminished elastic recoil of older subjects results in

reduced pulmonary pressure at given lung volumes (Mead,










Turner, Macklem, & Little, 1967). Reduction in pulmonary

pressure means that less air needs to be driven out of the

lungs during exhalation in order to achieve a balance with

atmospheric pressure.

Reduced elastic recoil and pulmonary pressure within

the lung do not affect total lung volume, which is corre-

lated with the height rather than the age of the person

(Bates & Christie, 1955; Dhar et al., 1976; Pierce & Ebert,

1965; Turner et al., 1968). Increased functional residual

capacity allows total lung volume to remain constant when

the elastic tissue changes reduce vital capacity

(Greifenstein et al., 1952; Mead et al., 1967; Pierce &

Ebert, 1965; Turner et al., 1968). This arrangement of

increased functional residual capacity and decreased vital

capacity results in a reduction of the volume of air

available for speech.

Reduced vital capacity and air volume may result in

lower intensity levels for the speech produced (Kahane,

1981). Ptacek et al. (1966) found significantly lower vital

capacities, peak intraoral air pressure, and peak intensity

levels for their older subjects than for their younger

subjects. These investigators concluded that a relation-

ship existed between the lower vital capacity and the

lowered levels of both peak intraoral air pressure and

intensity of the speech produced by their older speakers.

However, W. Ryan (1972) found that older speakers spoke with

a higher intensity level than younger speakers. This










difference indicates that aging changes in the respiratory

system may not make a crucial difference in speech

intensity.

Phonatory system

The phonatory system consists of the cartilages,

muscles, and mucosa of the larynx (Zemlin, 1968). Each of

these tissues exhibits an aging pattern that may affect

speech timing, intraoral air pressure magnitudes, and speech

intensity.

Cartilage. The cartilaginous framework of the larynx

undergoes ossification with aging (Kahane, 1983; Kahane,

Stadlan, & Bell, 1979; Noback, 1949; Zemlin, 1968).

Ossification begins during the second decade of life and

progresses with age, beginning low on the cartilage and

progressing caudocranially (Kahane, 1983; Kahane et al.,

1979; Noback, 1949). This process is more pronounced for

the hyaline cartilages, thyroid, cricoid, and arytenoid,

than for the elastic cartilage of the epiglottis (Kahane,

1983; Kahane et al., 1979; Zemlin, 1968). Ossification of

the hyaline cartilages is significant because these carti-

lages anchor the intrinsic laryngeal muscles that are

involved in phonation. Cartilage ossification may reduce

the nonmuscular forces in the larynx that depend on the

Spring action of the thyroid/cartilage by compressing the

thyroid cartilage (Kahane, 1981, 1983). This process could

slow vocal fold movement.










Slowing laryngeal activity can alter speech timing,

intraoral air pressure magnitudes, and vocal intensity.

These effects would result from changes in the relationship

between the phonatory and either the articulatory or the

respiratory system. Varying the temporal relationship

between the phonatory and articulatory systems would affect

voice onset time and voiced phonemes. These changes could

affect the meaning of the speech produced. Varying the

temporal relationship between the phonatory and respiratory

systems could result in loss of air and inefficient use of

the available air. This air loss could reduce magnitudes

of both intraoral air pressure and vocal intensity, since

the expiratory air is the driving force behind both of these

parameters. Similar effects on speech timing, intraoral

air pressure magnitudes, and vocal intensity may be noted

for age-related differences in the muscles and mucosa of the

phonatory system.

Muscles. Aging changes within the intrinsic laryngeal

musculature include atrophy (Bach, Lederer, & Dinolt, 1941;

Ferreri, 1959; Hirano, Kurita, & Nakashima, 1983), fiber

breakdown (Bach et al., 1941; Segre, 1971), and reduction of

blood supply (Bach et al., 1941; Ferreri, 1959). The effect

of these changes on the laryngeal muscles has been a subject

of much debate. Ferreri (1959) reported that the atrophied

vocal fold mass would vibrate more quickly and produce a

higher fundamental frequency. In contrast, Segre (1971)

focused on the fibrous breakdown of the thyroarytenoid










muscle and stated that the predominant effect of age on the

larynx is increased vocal fold flaccidity that results in a

lower fundamental frequency.

Cross-sectional studies of the fundamental frequency of

adult females have revealed two trends: one of relative

stability across age groups (Gilbert & Weismer, 1974;

McGlone & Hollien, 1963) and one of lower speaking funda-

mental frequency among older women (Benjamin, 1981; de Pinto

& Hollien, 1982; Stoicheff, 1981). This discrepancy of

results would best be resolved with more longitudinal data,

which may indicate the effects of age-related anatomic

changes within the larynx on the voice.

Reduced mass or increased flaccidity of the intrinsic

laryngeal muscles could result in significant temporal

changes in the speech signal. Either of these variations in

the vocal fold musculature could affect the timing of vocal

fold closing, which could result in a variation in

fundamental frequency.

Perhaps more important to the integrity of the speech

signal are the effects of the potential loss of synchron-

icity between the phonatory system and the other speech

systems. Structural alterations observed in laryngeal

muscles from older subjects, such as atrophy (Bach et al.,

1941; Ferreri, 1959; Hirano et al., 1983) and fiber breakdown

(Bach et al., 1941; Segre, 1971), could cause the glottis to

be open for longer periods of time. This could result in

inefficient use of the air from the respiratory system.










Less efficient air usage would reduce the amount of air

available as the driving force behind intraoral air pressure

and speech intensity. Altering the timing relationship

between the phonatory and articulatory systems could affect

all phonemes that require voicing. This would most notably

affect voice onset time and phoneme duration, which are

paramount in the accurate production of speech (Lisker &

Abramson, 1964; Muller & Brown, 1980; Umeda, 1977).

Mucosa. The mucosa consists of the epithelium and

lamina propria that line the lumen of the larynx (Hirano et

al., 1983). These authors defined the vocal ligament as the

thickening of the intermediate and deep layers of the lamina

propria at the glottal margin. Elastic fibers comprise the

intermediate layer and collagen fibers comprise the deep

layer of the laimina propria. Histological studies of the

structure of the vocal ligament have revealed age-related

differences in adults (Ferreri, 1959; Hirano et al., 1983).

Ferreri (1959) reported reduced elastin in the extracellular

network of the vocal folds and an increase in fatty deposits

in vocal folds from subjects over 70 years old. Hirano et

al. (1983) found that the pattern of reducing elastic fibers

combined with increasing collagen tissue resulted in a

reduction in extracellualr connective tissue in the vocal

folds from the second through sixth decade of life followed

by an increase in extracellular fibers in the vocal folds

from the sixth through ninth decade of life.










The reduced number of more pliant elastic fibers

combined with an increase in the stiffer collagen fibers

creates a stiffer vocal ligament. In addition, Kahane

(1983) reported that the increased proportion of collagen

fibers results in a "wavy" medial border of the vocal fold.

This finding is consistent with reports that the vocal folds

of older subjects are bowed at midline (Honjo & Isshiki,

1980; Segre, 1971). The wavy, bowed, and stiff appearance

of the vocal ligaments may also be affected by a general

drying of the mucosa.

The outer, epithelial layer of the mucosa is signifi-

cantly drier in older subjects than in younger ones

(Ferreri, 1959). Drier mucosa presents a thin, yellowish

appearance when viewed laryngoscopically (Segre, 1971). The

drying and thinning of the epithelial layer of the vocal

folds in older subjects may stiffen the structures and may

alter the midline of the vocal folds (Kahane, 1981, 1983).

These mucosal alterations could result in the bowing of the

vocal folds described by Honjo and Isshiki (1980) and Segre

(1971). Bowing at the midline of the vocal folds may cause

inefficient vocal fold closure and reduced subglottal

pressure (Kahane, 1983). Inefficient air usage at the

glottis could result in reduced air pressure in the oral

cavity and less sound pressure in the air.

In a similar manner, the indices of speech timing may

be affected by the structural changes within the laryngeal

mucosa. The stiffening of the mucosa may alter the timing










between the larynx and the articulators by increasing the

time it takes for the vocal folds to close and thus affect

speech timing. This prolongation of voicing time may

cascade into prolongation of other phonemes. Thus, slowed

timing between the phonatory and articulatory systems could

result in prolongations of phoneme duration.

Articulatory system

The articulatory system consists of three connected

tubes: the laryngopharynx, oropharynx, and nasopharynx.

Valving points of articulation within these tubes are the

velopharyngeal port, the back, blade, and tip of the tongue,

the teeth, the lips, and the jaw (Zemlin, 1968). Aging

changes of the latter list of structures consist mainly of

involution and atrophy (Kahane, 1981).

Teeth and mandible. The most noticeable change to the

oral structure for many older people is the loss of teeth.

Kaplan (1971) reported that 50% of all Americans have

lost their teeth by age 65, and that tooth loss increases to

67% by age 75. The main cause of tooth loss among

the elderly is periodontal disease (Kaplan, 1971; Klein,

1980). Klein (1980) reported that 97% of people over

45 years old have some degree of periodontal disease.

Loss of natural teeth has been associated with involu-

tion of the toothless, or edentulous, jaw (Goldstein, 1936;

Kaplan, 1971; Klein, 1980). Goldstein (1936) found that his

older subjects, 80% of whom were edentulous, had

reduced mandibular height from alveolar resorption. The








16

subjects also had an increased angle to the ramus that moved

the entire mandible forward relative to the face. In con-

trast, the results of a longitudinal study by Israel (1973)

indicated that the mandible, along with the rest of the

craniofacial bones, continues to grow slowly throughout

adulthood. Israel (1973) found that the mandible increases

in size by approximately 5% between the thirtieth

year and sixtieth year. He also stated that aging itself

was not a factor in mandible resorption. However, he did

not include subjects who were over age 65, leaving his

conclusions concerning aging and mandible resorption

incomplete.

The reduction of mandibular mass of the edentulous

person could alter the shape and size of the oral cavity.

Such an alteration of the cavity is likely to have an effect

on tongue carriage and the ability of the tongue to make

correct articulatory contact. These physiologic changes may

cause slower oral motor activity and prolonged phonemes.

Tongue. Studies of the tongue have revealed age-related

differences in both sensory and motor functioning. The

tongue does not atrophy with aging as most striated muscles

do (Balogh & Lelkes, 1961; Kaplan, 1971; Klein, 1980; Price

& Darvell, 1981). In fact, the size of the tongue increases

in edentulous oral cavities (Balogh & Lelkes, 1961; Kaplan,

1971; Klein, 1980; Price & Darvell, 1981). While Kaplan

(1971) and Klein (1980) reported clinical impressions that










the tongue loses muscle tone with aging, Price and Darvell

(1981) found no evidence of this among specimens at autopsy.

The maximum suction created by older subjects with their

natural teeth, or dentate older subjects, was significantly

less than that created by the dentate younger subjects.

However, the edentulous older subjects generated signifi-

cantly more suction than either dentate group (Price &

Darvell, 1981). Thus, the edentulous older subjects that

Kaplan (1971) and Klein (1980) described as exhibiting

reduced muscle tone were found to have increased tongue

force by Price and Darvell (1981). These authors reasoned

that the edentulous person uses the tongue to greater and

more varied purposes during mastication and deglutition than

does the dentate person.

Older dentate and edentulous subjects are equally

susceptible to reduced sensitivity to taste (Balogh &

Lelkes, 1961; Corso, 1975; Kaplan, 1971; Klein, 1980). The

reduced sensitivity occurs among all four of the basic

tastes: sweet, sour, bitter, and saline (Balogh & Lelkes,

1961; Corso, 1975; Kaplan, 1971; Klein, 1980). One might

assume this would imply a general reduction of perception on

the tongue. While Balogh and Lelkes (1961) found that to be

true for some older subjects, others reported an increased

sensitivity to touch and pain. The increased sensitivity

was related to increased friction during tongue movement

caused by a reduced moisture level (Balogh & Lelkes, 1961).










The physiologic differences caused by aging of the

tongue may influence speech production. In a study of

maximum tongue excursion for phonating /a/, /i/,and /k/,

Sonies, Baum, and Shawker (1984) found that the tongues of

dentate older subjects exhibited significantly less

posterior movement in articulating /a/ than the tongues of

younger subjects. No significant differences in tongue

movement were noted between the groups for production of /i/

or /k/. Once the tongue achieves the phonemic position,

age-related muscular changes may be responsible for the

reduced ability to hold maximum intraoral air pressure

(Ptacek et al., 1966). In addition, the muscular changes

may also affect the timing of speech.

Diadokokinetic rate is an indicator of speech timing

that is related to phoneme duration (Fletcher, 1972). The

faster a person moves the tongue to repeat a phoneme, the

shorter the minimum duration of that phoneme for that per-

son. While some investigators have found that both male and

female older subjects exhibit slower diadokokinetic rates

than younger subjects (Price & Darvell, 1981; Ptacek et al.,

1966), Shanks (1970) found no significant differences in

diadokokinetic rates among three age groups of women.

The differing results for diadokokinetic rate among

older speakers may be related to several factors. One

possible factor is the varying ability of the experimenters

to motivate older subjects to perform maximally on the task

(Ptacek et al., 1966). A second source of variability may










be the use of different syllables by each experimenter.

Varying the stimulus syllables meant that different tongue

movements were involved, making direct comparisons

difficult. Finally, the finding among older subjects of a

slower diadokokinetic rate (Price & Darvell, 1981; Ptacek et

al., 1966) may be related to the findings of reduced tongue

excursion (Sonies et al., 1984) and slower speaking rate

(Hollien & Shipp, 1972; Mysak, 1959; Mysak & Hanley, 1959;

Ptacek & Sander, 1966; W. Ryan, 1972; W. Ryan & Burk, 1974).

These behaviors could all indicate reduced tongue mobility

among older subjects that could affect speech timing,

intraoral air pressure magnitudes, and vocal intensity.

Oral mucosa. The oral mucosa exhibits atrophy and loss

of elasticity in older subjects, primarily because of a

reduction of saliva (Corso, 1975; Kaplan, 1971; Klein,

1980). Klein (1980) reported that the drying of the mucosa

would increase the friction during intraoral movements.

Increased friction during intraoral movement would tend to

reduce the speaking rate and increase phoneme duration.

Lips. The lips become wrinkled and drawn on older

subjects. Two factors have been reported to account for

these changes. Kaplan (1971) noted that the lips become

drier with age, particularly for edentulous people, while

Klein (1980) stated that the lip musculature becomes weaker

with age. Of these aging effects, the weaker musclature

would affect speech to a greater degree. Weakening of the










lip musculature would reduce the ability to maintain intra-

oral pressure during the production of /p/ and /b/. Lip

muscle weakness would also slow lip movements, prolonging

phoneme duration and reduce voice onset time.

Oral sensation. Kahane (1981) reported that while

several studies describe oral sensation and perception of

young adults, a paucity of research exists on the oral

sensitivity of older subjects. He stated that one should be

able to safely generalize findings of perception and sensa-

tion declines from similar body tissues to the oral struc-

tures. These declines would be consistent with the reduced

speed of receptive neural transmission described by LaFratta

and Canestrari (1966). Age-related declines in oral

perception and sensation may reduce articulatory feedback

(Kahane, 1981).

Oral perception and sensation changes could alter

speech timing, intraoral air pressure magnitudes, and speech

intensity. Reduced oral perception and sensitivity may

alter speech timing by increasing the duration needed to

recognize achievement of phonetic placement. A timing

change would increase phoneme duration as well as alter the

relationship with the larynx as indicated by voice onset

time. The ability to perceive pressure levels could be

reduced by the change in oral perception and sensation.

Reduced perception may result in an increased level of

intraoral air pressure and speech intensity during conver-

sational speech as was found by W. Ryan (1972).










Effects of Age-Related Physiologic Differences on Speech
Timing, Intraoral Air Pressure Magnitudes, and Vocal
Intensity

The previous discussion described the age-related

physiologic differences that occur in the respiratory,

phonatory, and articulatory systems of the speech production

mechanism. Within each system, these differences were shown

to have a potential effect on speech timing, intraoral air

pressure magnitudes, and vocal intensity. The degree to

which aging affects these three speech parameters is not

known.

If the aging changes within the speech production

mechanism significantly reduce the ability to correctly time

the speech, such differences probably would alter the

intelligibility of the speech. When alterations among the

stream of sounds occur, there is a breakdown between the

speaker's intended message and the actual message sent.

This breakdown may be the basis for the percept of age

differences among speakers. Aging changes in the speech

production mechanism may create such a breakdown.

Aging changes within the speech production mechanism may

significantly reduce the ability to develop pressure during

speech; this reduction would alter the projection of the

speech signal. Since the air stream from the respiratory

system is the power source that drives speech production,

reductions in that air stream would diminish the effective

radius of the speech signal. Thus, investigation of the










age-related differences within the speech production mech-

anism may reveal significant differences in speech timing,

intraoral air pressure magnitudes, and vocal intensity.

Alterations of speech timing, intraoral air pressure

magnitudes, and vocal intensity associated with aging have

been investigated using mainly perceptual and acoustic

variables. These studies have been limited in number and

vary in methodology. The varying methodologies may have

been a factor in the differing results among some of the

studies.

Speech Timing

Timing differences between older and younger adult

speakers have been consistently reported in both perceptual

and acoustic studies. Listeners report that a reduced rate

is among the principal perceptual features that mark the

speech of older adults (Hartman, 1979; Hartman & Danhauer,

1976; Ptacek & Sander, 1966; E. Ryan & Capadano, 1978; W.

Ryan & Burk, 1974). Acoustic studies that measured the

ratio of phonation time to total speaking time (Mysak, 1959)

and words per minute (Mysak, 1959; Mysak & Hanley, 1959; W.

Ryan, 1972) found a slower speaking rate among geriatric

subjects. The specific variables of speech timing that are

involved in the slower speech rate have yet to be fully

enumerated.

A few studies have investigated the effect of specific

timing variables on the slower speech rate of older people.

Benjamin (1982) reported that the speech of older speakers










is marked by longer vowel durations, longer stop consonant

durations, and shorter voice onset times. The vowel dura-

tion information was appropriately separated into stressed

and unstressed vowels, but the consonant information was

not divided into voiced and voiceless consonants. Since

consonant timing differs by voicing, these relative differ-

ences may change with age. Thus, the information available

from dividing the consonants into voiced and voiceless

categories may provide valuable information concerning age

differences in consonant timing.

The voice onset time information provided by Benjamin

(1982) differs from that previously reported. While she

reported reduced voice onset times among older speakers,

other studies reported no significant duration differences

between older and younger adult speakers (Neiman et al.,

1983; Sweeting & Baken, 1982). However, a closer analysis

of the data of Neiman et al. (1983) revealed that when the

different vowel conditions were separated, the older speakers

had significantly shorter voice onset times than did the

younger speakers. Since Benjamin (1982) did not report

which stop consonants she measured, direct comparisons of

the results of the studies are difficult. Sweeting and

Baken's (1982) finding of increased variability of voice

onset time among older speakers has not been corroborated by

other studies of voice onset time among older subjects.

Thus, the three studies of the voice onset time of older

speakers have differing patterns of results. Benjamin










(1982) and Neiman et al. (1983) reported shorter durations

among older subjects, while Sweeting and Baken (1982)

reported no differences. In contrast, Sweeting and Baken

(1982) reported increased voice onset time variability while

the others did not. The results of all three studies imply

that voice onset time may be a component of the perceived

difference between older and younger adult speakers.

Further investigation of the effect of aging on voice onset

time is needed to help clarify this relationship.

Stability of voice onset time durations across adult

age groups is counter-intuitive, given the reduced motoric

and neurologic rates that have been reported for older

adults (Birren, 1974; Welford, 1977). However, if the voice

onset time durations are found to be stable across age

groups, then the neuromotor function for the production of

voice onset time may be relatively impervious to the slower

motoric and neurologic rates reported by Birren (1974) and

Welford (1977).

In general, the reports from acoustic studies of age-

related differences in vowel duration, consonant duration,

and voice onset time may be related to the perceptual reports

of less precise articulation among older speakers (Hartman,

1979; Hartman & Danhauer, 1976; E. Ryan & Capadano, 1978; W.

Ryan & Burk, 1974).

Vocal Intensity and Intraoral Air Pressure Magnitudes

Less agreement exists between the perceptual and

acoustic studies of aging differences in vocal intensity








25

than was found for speech timing. Perceptual studies reveal

that listeners report reduced (Ptacek & Sander, 1966; E.

Ryan & Capadano, 1978) or unchanged (Ramig & Ringel, 1983)

intensity for older speakers. An acoustic study by W. Ryan

(1972) revealed increased intensity among older speakers.

In a study that measured intraoral air pressure among older

subjects, acoustic and physiologic measurement of maximum

effort revealed a reduction in both speech intensity and

intraoral air pressure (Ptacek et al., 1966). However,

difficulty exists in comparing studies of maximum and com-

fortable effort, so the maximum effort results do not alter

the discrepancy between the acoustic and perceptual studies

of comfortable loudness.

A possible factor in the discrepancy between the

acoustic and perceptual findings is that the age estimates of

the voices in the perceptual studies were under 60, while the

acoustic study described speakers over age 60. Thus, the

listeners could have been matching features to a stereotype

for middle aged rather than geriatric speakers (E. Ryan &

Capadano, 1978). Since a similar discrepancy between

acoustic and perceptual studies was not found for speech

timing, the pattern of aging differences may vary among the

speech parameters. An investigation that relates perceived

speaker age to speech timing, intraoral air pressure magni-

tudes, and vocal intensity may provide more complete infor-

mation concerning the effect of the age-related physiologic











differences within the speech production mechanism on the

speech produced.

A study of the age-related physiologic differences in

speech should include measures that will be indices of the

timing and pressure levels of the speech produced. The

intricate timing of the coordination of respiratory,

phonatory, and articulatory events to create speech may be

altered by aging of the component structures. The pressure

levels of speech may be compromised by the reduced vital

capacity of the lungs (Pierce & Ebert, 1965; Turner et al.,

1968) as well as the reduced muscular ability found among

older subjects (Dhar et al., 1976; Kaplan, 1971). The

variables determined as salient in age-related differences

of speech timing, intraoral air pressure magnitudes, and

vocal intensity from a physiologic study could then be

tested using perceptual and acoustic studies.

Measurement of Speech Timing, Intraoral Air Pressure,
and Vocal Intensity

Speech Timing

Two effective indices of the timing of speech are

phoneme duration and voice onset time. These variables

represent different aspects of the temporal dynamics of

speech. Phoneme duration provides an index of the ongoing

interphonemic relationship of coarticulation. The temporal

pattern of articulatory constriction is indicated by conso-

nant duration and the timing of the transitions between the

constrictions is indicated by vowel duration. Aging effects










within either category of this index may reveal an age-

related discoordination among the articulators. Addition-

ally, increased variability of phoneme duration in repeated

syllables among the older speakers may indicate a reduced

ability to consistently position the articulators.

While phoneme duration is an index of temporal factors

among the articulators, voice onset time is an index of the

temporal factors between the phonatory and articulatory

systems (Lisker & Abramson, 1964, 1967; Zlatin, 1974).

Increased or decreased voice onset time would indicate a

change in the interaction of the phonatory and articulatory

mechanisms. Similarly, an increased variability in voice

onset time among older adults may indicate a reduced ability

to consistently maintain the fine degree of inter-systemic

interaction required for speech. Thus, the temporal indices

of phoneme duration and voice onset time may provide strong

indications of a temporal component in age-related speech

differences.

Phoneme duration

Phoneme duration has been examined in two categories:

consonant duration and vowel duration. For this investi-

gation consonant closure duration was operationally defined

as the time interval beginning with the increase of intra-

oral pressure from baseline and ending with the drop of

intraoral pressure at consonant release.

The operational definition of vowel duration for this

investigation was the time interval beginning with the onset











of voicing after the consonant release and ending with the

offset of voicing. Both consonant closure duration and

vowel duration are strongly affected by the contiguous

phonemes, as well as such factors as stress and place in

word, phrase, and utterance.

Consonant duration. Consonant duration in connected

speech is inextricably bound to the relationship between the

consonant and its phonetic environment (Flege & Brown, 1982;

Klatt, 1973; Lehiste, 1972; Malecot, 1968; Miller, 1981;

Oller, 1973; Port, 1981; Schwartz, 1972; Stathopoulos &

Weismer, 1983; Umeda, 1977; Van Hattum & Worth, 1967).

Location within a word is an important variable for stop

consonant durations, with word initial and word final conso-

nants being more affected by their location within the word

than by their vowel environment (Umeda, 1977). Oller (1973)

reported that, given similar vowel environments, word

initial stop consonants have a greater duration than word

medial stop consonants and word final stop consonants have a

greater duration than word initial stop consonants. This

pattern has been found at the phrase level also (Umeda,

1977; Van Hattum & Worth, 1967). In contrast, Stathopoulos

and Weismer (1983) found word initial stop consonants to

have the greatest durations followed by medial and final

word positions.

Consonant duration varies systemically by place of

articulation (Lehiste, 1972; Repp, 1984; Stathapoulos &

Weismer, 1983; Umeda, 1977), with labials having the longest








29

duration, then apicals and the shortest durations among the

velars. However, in the intervocalic position, the apical

consonants exhibit the shortest duration (Lehiste, 1972;

Umeda, 1977). Closure duration is generally longer for

voiceless stop consonants than for their voiced cognates

(Brown, 1979; Lisker, 1957; Muller & Brown, 1980; Sharf,

1962; Subtelny et al., 1966). The reported exceptions are

intervocalic /t/ and /d/ which are both taps (Muller &

Brown, 1980) and word initial stop consonants before a

stressed vowel (Stathopoulos & Weismer, 1983).

The pattern of stop consonant durations in words and

sentences is similar, with initial and final stop consonant

durations being greater than those for medial stop conso-

nants (Schwartz, 1972; Umeda, 1977, Van Hattum & Worth,

1967). Temporal variables, such as stress, contiguous vowel

duration, word length, and phrase length alter consonant

duration (Port, 1981). For example, stop consonants are

longer both before and after stressed vowels in comparison to

unstressed vowels (Malecot, 1968; Stathopoulos & Weismer,

1983; Subtelny et al., 1966). Additionally, closure duration

of initial stop consonants decreases with increased word

length and with increased phrase length (Schwartz, 1972;

Umeda, 1977). While many variables may affect consonant

duration, vowels are responsible for most of the difference

in total utterance duration that occurs during a change in

speaking rate (Gay, 1978; Miller, 1981).










Vowel duration. As shown for consonants, several

factors influence vowel duration for young adult speakers.

The principal factors are vowel tenseness, phonetic context,

stress, utterance length, and speaking rate (House, 1961;

House & Fairbanks, 1953; Lehiste, 1972; Klatt, 1973; Miller,

1981; Peterson & Lehiste, 1960; Sharf, 1964; Umeda, 1975).

While realizing that none of these factors operates

independently during running speech, the contribution of

each to vowel duration will be described individually.

In English, vowels can be separated into two categories,

tense and lax. The tense vowels, /i/, /u/, /o/, /e/, /a/,

/s/, and /o/, have relatively long durations and the lax

vowels, /I/, /n/, /A/, and /e/, have relatively short

durations (House, 1961; Sharf, 1964). When Verbugge and

Isenberg (1978) created complex waves with vowel formant

values between those for /e/ and /e/ and then manipulated

the durations of the formants, they found that their

listeners heard the short durations as /s/ and the long

durations as / /. This demonstrates the importance of vowel

duration in the recognition of vowels.

Post-vowel consonants affect vowel duration in English.

Principally, vowels preceding voiceless consonants are of

shorter duration than vowels preceding voiced consonants

(House, 1961; House & Fairbanks, 1953; Klatt, 1973; Peterson

& Lehiste, 1960; Sharf, 1962, 1964). A second factor

affecting vowel duration is that vowels preceding fricative

consonants have longer durations than those preceding stop










consonants (House, 1961; House & Fairbanks, 1953; Klatt,

1973; Peterson & Lehiste, 1960; Sharf, 1964). In contrast,

the place of articulation of the consonant following the

vowel has no significant effect on the vowel duration

(Sharf, 1964). Additionally, consonants that precede vowels

have no consistent effect on vowel duration (Peterson &

Lehiste, 1960).

Vowels in stressed syllables are longer than those in

unstressed syllables (Lehiste, 1972; Umeda, 1975). At the

sentence level, vowels in stressed words have longer

durations than those in unstressed words (Peterson &

Lehiste, 1960; Port, 1981). These vowel duration effects

from stress are closely related to those from length of

utterance and rate of speech (Gay, 1978).

As word length increases, the duration of the vowels

within the word decreases; the same effect was found at the

sentence level (Klatt, 1973; Lehiste, 1972; Port, 1981).

Lehiste (1972) also reported that vowel durations are

shorter in syllables at the beginning of phrases than at the

end of phrases. A limiting factor of these variations is

that each vowel has a minimum duration, beyond which there

can be no further reduction (Klatt, 1973; Port, 1981). The

minimum phoneme duration is consistent across increased

utterance length and increased speaking rate (Port, 1981).

When speaking rate is altered, the most variable portion

is the vowel duration (Gay, 1978; Miller, 1981). Miller

(1981) stated that increased speech rate not only reduces











absolute vowel duration but also reduces relative vowel

duration. He found a greater reduction in the duration of

tense vowels than in the duration of lax vowels, thus

reducing the difference between tense and lax vowels. When

the speech rate is altered, the listener alters the duration

parameters for perception of vowels (Verbugge & Shankweiler,

1977). These authors reported that for a given rate of

speech there are established duration parameters for vowels.

If those parameters are violated, the vowel will be

incorrectly perceived.

As the preceding discussion indicates, phoneme duration

is a complex index of speech timing. In order to effec-

tively utilize phoneme duration as an index of speech

timing, several controls are needed. Since Umeda (1977)

reported that word position is important for consonants,

this will need to be systematically varied while maintaining

a similar vowel environment (Oller, 1973). Different places

of articulation (Lehiste, 1972; Umeda, 1977) and both voiced

and voiceless consonants (Brown, 1979; House, 1961; House &

Fairbanks, 1953; Klatt, 1973 Lisker, 1957; Muller & Brown,

1980; Sharf, 1962, 1964; Subtelny et al., 1966) are also

needed in order to effectively measure phoneme durations.

By investigating consonant and vowel durations under these

conditions, specific speech timing information can be

obtained.










Voice Onset Time

The other index of speech timing, voice onset time,

reveals different speech timing information than phoneme

duration. While phoneme duration involves primarily

articulatory events, voice onset time involves the inter-

action of articulatory and phonatory events. By using voice

onset time as an index of speech timing, the age differences

in two components of the speech production mechanism may be

examined during stop consonant production.

Voice onset time is the difference between the onset of

quasi-periodic oscillation of the vocal folds and oral

release of the consonant (Lisker & Abramson, 1964; Zlatin,

1974). Significant differences of voice onset time occur

with changes of voicing and place of articulation

(Abramson, Lisker, & Cooper, 1965; Flege, 1982; Klatt, 1975;

Lisker & Abramson, 1964, 1967; Smith, 1978). The differ-

ences between the voice onset times of voiced stop conson-

ants and their voiceless cognates are consistently signifi-

cant in English and in other languages (Lisker & Abramson,

1964). The consonants /b/, /d/, and /g/ are characterized

by voice onset times that range from prevoicing, or vocal

fold oscillation before consonant release, to voicing that

lags shortly behind the release of the consonant. Their

homorganic cognate consonants /p/, /t/, and /k/ are charac-

terized by voice onset times having a considerably greater

lag of voicing after the consonant release (Abramson et al.,











1965; Flege, 1982; Klatt, 1975; Lisker, 1957; Lisker &

Abramson, 1964, 1967; Smith, 1978).

Besides separating stop consonants by voicing, voice

onset time differences can consistently separate stop

consonants by place of articulation (Klatt, 1975; Lisker &

Abramson, 1964, 1967; Zlatin, 1974). Voice onset times are

shortest for labial stops, then apical stops, and are

longest for velar stops (Lisker & Abramson, 1964, 1967;

Zlatin, 1974).

In measuring voice onset time, the same controls are

relevant as they are for phoneme duration. For both indices

of speech timing the voicing contrast and place of articula-

tion are important variables. The two indices should reveal

subtle variations in speech timing that result from the

age-related physiologic differences in the speech production

mechanism.

Intraoral Air Pressure

Investigation of the phonetic differences in intraoral

air pressure have been reported as long ago as Rousselot

(1897). Phonetic importance was ascribed to intraoral air

pressure pulses by Stetson (1951), who stated that the

syllable was the basic unit of speech production. The

pressure pulse was further investigated by Black (1950) who

reported that voiceless stop consonants exhibit greater peak

intraoral pressure values when compared to their voiced

cognates. Over the past thirty years the equipment used to

determine intraoral air pressure has been improved and shown










to be more reliable (i.e., Arkebauer et al., 1967; Brown,

1979; Subtelny et al., 1966).

Intraoral air pressure has proven to be an effective

means for measuring physiological differences among

phonemes. Information gathered from measuring intraoral air

pressure includes peak magnitudes of intraoral air pressure,

consonant durations, and vowel durations (i.e., Arkebauer et

al., 1967; Brown, 1979; Brown & McGlone, 1969a; Brown &

McGlone, 1969b; Subtelny et al., 1966).

Phonetic differences between stop consonants have been

reported in intraoral air pressure studies. The most fre-

quently reported finding is greater peak amplitudes of the

pressure pulse for voiceless consonants than for their

voiced cognates (Arkebauer et al., 1967; Bernthal &

Beukelman, 1978; Black, 1950; Brown, 1979; Brown & McGlone,

1969a, 1979; Brown, McGlone, Tarlow, & Shipp, 1970; Karnel &

Willis, 1982; Klich, 1982; Lisker, 1957; Malecot, 1955,

1966a, 1966b, 1968; Netsell, 1969; Subtelny, Worth, &

Sakuda, 1966; Tatham & Morton, 1973; Warren, 1964; Warren &

Hall, 1973). Several investigators (Arkebauer et al., 1967;

Black, 1950; Brown, 1979; Malecot, 1955; Subtelny et al.,

1966) also reported that the peak intraoral pressure assoc-

iated with the production of stop consonants is greater than

that for fricative consonants. Word initial and word medial

stop consonants exhibit greater peak pressure values than

word final stop consonants (Arkebauer et al., 1967; Brown,

1979; Brown et al., 1970; Dixit & Brown, 1978; Malecot, 1968;










Subtelny et al., 1966;). Additionally, peak intraoral air

pressure values increase with increases in speech intensity

(Arkebauer et al., 1967; Brown & Brandt, 1971; Brown et al.,

1973; Hixon, 1966). Brown et al. (1973) reported that the

peak intraoral pressure associated with consonants is sensi-

tive to the vowel context, with peak pressure values being

greater for consonants preceding /i/ than for those preced-

ing /u/, which are greater than those preceding /a/. Peak

intraoral pressure values for consonants have been reported

to be stabile between presentations in syllables and in

words as well as across repeated productions (Brown &

McGlone, 1969b; Brown & Shearer, 1970; Murry & Brown, 1976).

The phonetic differences that are evident from peak intra-

oral air pressure are found among children as young as six

years old and remain relatively stable into adulthood

(Arkebauer et al., 1967; Brown, 1979).

A natural extension of the above studies is to find if

the peak intraoral pressure values are different for older

subjects. The known changes in perioral mucosa, muscula-

ture, and innervation (Kaplan, 1971; Klein, 1980) may affect

both the ability to generate peak intraoral pressures and

the ability to sense the intraoral pressures that have been

generated. Age-related alterations of perioral sensation

may be qualitatively different from the anesthetically

induced loss of perioral sensation previously investigated

(Prosek & House, 1975; Ringel & Steer, 1963; Scott & Ringel,

1971). The use of anesthetic to block perioral receptors








37

did not result in significant differences in peak intraoral

air pressure or consonant durations. Perhaps the age-

related reductions in neural behavior combined with the age

related changes to the oral musculature and mucosal systems

result in significant reductions in peak intraoral air

pressure values among older adult speakers.

For a nonspeech task, Ptacek et al. (1966) reported

that maximum intraoral pressure as measured by a U-tube

manometer was significantly reduced for older speakers in

comparison to younger speakers. However, the nonspeech task

of maximum intraoral pressure requires none of the precision

or short duration involved in normal articulation.

Leeper and Noll (1972) found intraoral air pressure and

speech intensity varied directly with effort level. Simi-

larly, Brown and Brandt (1971, 1972) reported that, under

masking, their subjects increased intraoral air pressure

concomitant to increases in sound pressure level. Results

of these studies indicate a strong relationship between

speech effort and intraoral air pressure and vocal inten-

sity. Together, the two variables provide a physiologic

measure that is closely related to an acoustic measure.

Vocal Intensity

Studies of vocal intensity frequently relate intensity

to a physiologic variable, possibly because of the

difficulty in producing consistent vocal intensity levels

(Leeper & Noll, 1972). These authors found that even when

subjects attempt to control their effort level, vocal








38

intensity level exhibits great variability. In a series of

studies on "comfortable" loudness levels, Brown and his

associates (Brown, Murry, & Hughes, 1976; Murry & Brown,

1983) have found within session vocal intensity to be more

consistent than between session vocal intensity. They

found that between session vocal intensity varied as much

as 25 dB over five days within a single subject. Addition-

ally, Rubin et al. (1967) reported that intersubject

variability of vocal intensity is greater than intrasubject

variability.

The physical properties of the radiating source of the

speech as well as the proximity of the microphone affect the

recording of vocal intensity (Hixon, 1966; Rubin et al.,

1967). The greater the cross-sectional area of the open

mouth, the greater is the intensity (Hixon, 1966; Isshiki,

1965), and reducing the mouth-to-microphone distance by

half increases the intensity by 6 dB (Rubin et al., 1967).

While controlling the mouth opening is difficult during

running speech, a need for controlling the mouth-to-

microphone distance when recording vocal intensity is

indicated.

Vocal intensity has been compared to physiologic

variables such as subglottal air pressure, intraoral air

pressure, and air flow. The most consistent finding is that

increases in subglottal air pressure are accompanied by

increases in vocal intensity (Hixon, 1966; Isshiki, 1964,

1965; Ladefoged & McKinney, 1963; Rubin et al., 1967).










Hixon (1966) also reported that changes in vocal intensity

are always accompanied by changes in intraoral air pressure.

In contrast to the findings for the two air pressure mea-

sures, no clear relationship between air flow rate and

vocal intensity has been found in the modal register

(Isshiki, 1964, 1965; Rubin et al., 1967). Since no clear

relationship between air flow and vocal intensity has been

found and since measurement of subglottal air pressure is

highly invasive (Isshiki, 1964, 1965), intraoral air pres-

sure is a preferred variable to be used in conjunction with

vocal intensity. When intraoral air pressure and vocal

intensity are used in combination, an effective physiologic

and acoustic combination is achieved for measuring

age-related differences in speech.

Purpose

As previously expressed, there is an increased number

of older people in the population. As the number of older

people has increased, interest in investigating age-related

changes has increased also. In the field of phonetics, the

effects of age differences on the perception and acoustics

of speech have been studied.

Perceived aging effects upon speech production may

occur because of anatomic and physiologic changes within the

bony and cartilaginous skeleton, the muscular body, and the

protective mucosal covering (Kahane, 1981; Meyerson, 1976).

The alteration of each of these tissues with aging may cause

variations in speech timing, peak intraoral air pressure










magnitudes, and speech intensity, parameters which may

affect the effectiveness of communication.

Stiffening of the skeletal framework, atrophy of the

musculature, and drying of the mucosa of the speech

production mechanism are likely to alter the velocity of

these structures. Alterations in velocity can be measured

by indices of speech timing. Since older speakers exhibit

slower rate of speech (Mysak, 1959; Mysak & Hanley, 1959;

W. Ryan, 1972; Shipp & Hollien, 1971), investigation of

specific components of the speech may determine the nature

of the slower speech. By measuring phoneme duration and

voice onset time, temporal variations of the component

phonemes and the relationship between consonants and the

contiguous vowels may be revealed. This information may

indicate if the slower rate of speech among older speakers is

related to slower velocities of the articulators or possibly

inertia in stopping and starting articulatory movements.

The voice onset times will also provide information

concerning the interaction of the articulatory movements and

the onset of vocal fold oscillation.

Similarly, the stiffening of the skeletal framework,

atrophy of the musculature, and breakdown and alteration in

the extracellular fibrous network within the speech

production mechanism could limit the pressures that may be

generated for speech. In fact, Ptacek et al. (1966) found

reduced maximum speech intensity levels among their older

adult subjects. However, W. Ryan (1972) reported increased










intensity for speech among his older subjects. These

divergent findings implicate different systems as being

important in determining the speech intensity of older

speakers. The discrepancy of these findings needs to be

resolved. This can be accomplished by measuring speech

intensity at comfortable, minimum, and maximum loudness

levels. The close relationship between intraoral air

pressure and speech intensity establishes a check of

reliabiliy between the physiologic and acoustic measures.

In this manner a valid indication of age-related differences

along these parameters will be provided.

As established throughout the previous discussion, the

age-related physiologic differences in the speech production

mechanism may affect speech timing, intraoral air pressure

magnitudes, and speech intensity. Phoneme duration and

voice onset time may reveal aspects of aging variations in

speech timing. These variables may be related to perceptual

features that listeners utilize when determining speakers

ages.

Listeners have demonstrated the ability to separate

taped voice samples of young adult speakers from those of

old adult speakers, and to discriminate adult speakers by

age decade (Hartman, 1979; Hartman & Danhauer, 1976; Ptacek

& Sander, 1966; E. Ryan & Capadano, 1978; Shipp & Hollien,

1969). While age differences are perceived in adult voices,

the specific features that vary across age groups are not

clear. The determination of the presence of age-related








42

differences in speech timing, intraoral air pressure magni-

tudes, and speech intensity may provide baseline data for

isolating features relevant to the perception of a speaker's

age.

Information concerning speech timing, intraoral air

pressure magnitudes, and speech intensity may be useful in

determining the relevant variables for future perceptual

studies of age-related speech differences. In addition,

the physiologic data will increase the knowledge concerning

the normal changes that occur in speech over the course of

adult aging. This information will be useful for those

generating models of the effect of adult aging on the

communicative process.

The purpose of this investigation was to determine if

age-related physiologically based differences exist in the

speech of adult females. A perceptual study was completed

to determine if listeners could perceive the age differences

between the two populations.

Hypotheses

The following competing research hypotheses were tested:

1. Listeners can differentiate the two age groups of

speakers, but no age-related differences are found for the

relevant physiologic and acoustic variables.

2. Listeners can differentiate the two age groups of

speakers, and age-related differences are noted for the

relevant physiologic and acoustic variables.








43

3. Listeners cannot differentiate the two age groups of

speakers, and no age-related differences are found for the

relevant physiologic and acoustic variables.

4. Listeners cannot differentiate the two age groups of

speakers, but age-related differences are noted for the

relevant physiologic and acoustic variables.














CHAPTER III
METHODS

The increasing proportion of older adults in the popu-

lation has resulted in certain health related professions

exhibiting increased interest in age-related physiologic

differences in the speech mechanism. These physiologic

differences may be related to listeners' ability to deter-

mine the age of voices that they hear. The perceived age

differences may a result of age-related changes in the

respiratory, phonatory, and articulatory components of the

speech production mechanism. The reported physiologic

differences within the speech production mechanism may

significantly affect speech timing, intraoral air pressure,

and vocal intensity. Relevant indices of speech timing

include phoneme duration and voice onset time. By measuring

phoneme duration, voice onset time, intraoral air pressure,

and vocal intensity, it may be determined if the presence

of age-related physiologic differences within the speech

production mechanism affect the speech produced. This

information may be important for isolating the parameters

which are relevant to the perceived speech differences

between older and younger speakers.










Subjects

Speaking Task

The speakers were 50 ambulatory, Caucasian women

divided by age into two equal size groups consisting of 25

each. The first group included women aged 20 to 35 years,

who represented young adults. The second group included

women over 75 years of age, who represented old adults.

Since physiologic aging is evident by 70 years of age even

among healthy individuals (Hayflick, 1981), the women over

age 75 should exhibit the normal physiologic changes that

accompany advanced age. These two groups represent the

end-points of age-related differences in speech physiology.

By testing women at the end-points, this author assumes that

any possible age differences should be evident, without the

potential masking of the differences that may occur by using

women across the age span.

In order for health status to be held as constant as

possible across age groups, a short questionnaire (Appendix

1) and a hearing screening were used to determine if the

women meet the following criteria:

1) The women were capable of maintaining an independent

household, or were independent living.

2) They reported no history of bronchial asthma,

emphysema, or other respiratory disease.

3) The women had no reported history of aphasia or

other neurologic disorders affecting the speech or

phonatory mechanism.










4) They reported no history of senile dementia or

psychopathology.

5) They had no reported structural abnormalities of the

laryngeal mechanism.

6) They exhibited no articulation errors as determined

by a speech-language clinician during the reading of a

standard paragraph.

These criteria were chosen to help the investigator

minimize possible health variations between the two groups.

The first criterion refers to whether the subjects were

independent living. Lubinski (1981) reported reduced

language usage and reduced variety of utterances among older

people in nursing care facilities in comparison to those who

were independent living. The questions about the respira-

tory system were to reveal if that system was generally

intact. Since the respiratory system is the pump that

provides the air to drive the rest of the speech production

mechanism, information concerning the health status of this

system was needed. The remaining criteria addressed by the

questionnaire relate to the status of the phonatory and

articulatory portions of the speech production mechanism and

the relevant portions of the nervous system. These criteria

include appropriate voice, resonance, and articulation

skills.

The final criterion for the selection of subjects was

that they exhibit no hearing loss greater than 35 dB SPL in

at least one ear for the frequencies of 500 Hz, 1000 Hz, and










2000 Hz. An audiologic pure-tone screening was used to

determine if the potential subjects meet this criterion.

The selection of a 35 dB hearing loss in the better ear was

based on the National Health Survey of 1962, as reported by

Bergman (1980). This survey found that the median hearing

level for the better ear of women aged 75 through 79 years

was between 20 and 30 dB for the frequencies that were

screened during this investigation. In addition, Shanks

(1970) reported that the average hearing loss among 60 women

aged 60 through 80 years was 22 dB in the better ear and 28

dB in the worse ear. Shanks (1970) findings agree with

those summarized by Bergman (1980) from studies of the

hearing acuity of older women.

Listening Task

The listeners were two groups of 20 women each drawn

from the same age groups as the speakers. Women aged 20 to

35 years comprised the young group and women over age 75

comprised the old group.

In order to be included in the study, listeners had to

pass a multiple-choice rhyme-type speech discrimination test

(Griffiths, 1967) at 97% correct for the younger group and

84% correct for the older group. The lower speech discrimi-

nation criterion for the older listening group compensated

for the lower speech discrimination scores exhibited by

older people (Bergman, 1971; Goetzinger & Rousey, 1959;

Harbert, Young, & Menduke, 1966; Kasden, 1970; Punch &

McConnell, 1969). At the stated levels of performance, the










listeners in both groups exhibited normal speech discrimi-

nation for their age level. The speech discrimination of

listeners aged 20 to 35 years has ranged between 94 and 100%

(Bergman, 1971; Goetzinger & Rousey, 1959; Kasden, 1970),

while that for listeners aged 75 and over has ranged between

79 and 90% (Bergman, 1971; Goetzinger & Rousey, 1959;

Harbert, Young, & Menduke, 1966; Kasden, 1970; Punch &

McConnell, 1969). This selection criterion permitted the

investigator to infer that the listeners possessed adequate

hearing acuity for both the test instructions and the

experimental stimuli.

Equipment

Speaking Task

The system of measurement used while recording the

speakers in this study was particularly appropriate for the

parameters measured and the populations investigated. Brown

and his associates have demonstrated that intraoral air

pressure recordings provide an accurate method for measure-

ment of phoneme duration (Brown & Murry, 1976; Flege &

Brown, 1982; Muller & Brown, 1980), and when combined with a

laryngeal microphone, voice onset time (Flege & Brown,

1982). The intraoral air pressure and voicing signals were

recorded on separate channels of a system capable of storing

and presenting oscillographic displays of the two signals.

While the traditional method for measuring speech timing has

been spectrography, the oscillographic display has some

advantages over the spectrogram.








49

Brown (1985) discussed the advantages and disadvantages

of sound spectrography and oscillographic display of intra-

oral air pressure and voicing in the temporal measurement of

speech samples. Disadvantages that he reported for spectro-

graphy included a) the 2.4 second duration available for

each spectrogram is brief, b) the sample needs to be

recorded in a quiet environment, c) the phoneme boundaries

are often difficult to determine from the acoustic signal,

and d) accurate measurement of the spectrogram requires

experience. In contrast, the printed oscillographic display

has no duration constraint, does not require a quiet envir-

onment, provides clear examples of phoneme boundaries, and

is relatively easy to measure. Brown (1985) reported that

the principal advantage of the printed oscillographic

display is that the clarity of the phoneme boundaries makes

them easily measurable (Figure 1); in contrast, spectrogram

have potential difficulties in determining the delineation

of the onset and offset of phonemes (Figure 2).

In addition to providing a clear and accurate presen-

tation of the data, the methodology used was relatively

noninvasive. The insertion of a thin tube (outside diameter

2.82 mm) into the palatal vault to measure intraoral air

pressure was the most invasive aspect of the data collec-

tion. This method is not as invasive as the tracheal

puncture required for accurate determination of subglottal

pressure, the alternative method for measuring air pressure



















PI0' e









c d
GLOTTAL
PULSING





P a

a b








Figure 1. Representation of an oral air pressure trace and
voice signal for the syllable /pa/. The duration of conson-
ant /p/ is represented by points (a) and (b). A sudden
marked increase in air pressure denotes the onset of conson-
ant closure (a), while the consonant release is signaled by
a sudden drop in pressure (b). The duration of the vowel
/a/ is depicted by the points (c) and (d). The relationship
between the release of the consonant gesture and the onset
of voicing, voice onset time, is depicted by points (b) and
(c). Finally, the magnitude of the peak intraoral air
pressure is depicted by points (e) and (f).

















TYPE B/65 SONAGRAM KAY ELEMETRICS CO. PINE BROOK. N. J.


Figure 2. Spectrogram of the phrase "Speak /pa/ again."
Stop consonant release is at point (a) and the onset of
voicing is at point (b).










within the vocal tract. The researcher deemed the rela-

tively noninvasive status to be of particular importance in

insuring the participation of the older subjects. In

addition, the intraoral pressure pulse provided information

on phoneme duration that would not have been available from

subglottal air pressure measures. Thus, the less invasive

technology also provided more information along the para-

menters relevant to this study.

The equipment used in this experiment recorded the

intraoral air pressure signal, the voicing signal, and the

acoustic signal. A schematic drawing of the equipment array

for each of these signals is shown in Appendix B.

Intraoral Air Pressure. Intraoral pressure was

measured by a system beginning with a polyethlene tube

(inside diameter 1.79 mm, outside diameter 2.82 mm, and 25

cm long) that was inserted into the corner of the subject's

mouth. This tube was directed high into the palatal vault

in a manner such that the end of the tube was on a coronal

plane with the posterior margin of the hard palate and free

of contact with the surrounding oral structures. The tube

had holes bored near the end placed in the oral cavity, in

order to help prevent spurious pressure recordings (Hardy,

1965). The opposite end of this tube was connected to a

Statham PM6TC differential pressure transducer that sent

the signal to an Accudata 105 gage, and an Accudata 109 DC

amplifier. The amplified signal passed through a low-pass

filter with a cut off at 100 Hz to eliminate phonation










vibrations that would add quasiperiodic variability to the

pressure signal. The amplified and filtered signal was

directed to one channel of a Honeywell 1508A Visicorder.

The Visicorder is a light recording oscillograph that

creates permanent recordings by directing a light beam

reflected from a galvonometer onto light sensitive paper.

Intraoral pressure is an effective method for measuring

peak intraoral pressure (Arkebauer et al., 1967; Brown,

1979; Brown and Brandt, 1971; Brown and McGlone, 1969a;

Brown et al., 1970, 1973; Brown and Shearer, 1970; Malecot,

1955; 1966a; 1966b; 1968; Subtelny, 1966), consonant dura-

tion (Brown, 1979; Flege and Brown, 1982; Muller and Brown,

1980), and vowel duration (Flege, 1982). When intraoral air

pressure measurements are combined with laryngeal vibration,

voice onset time information is made available (Flege and

Brown, 1982).

Voicing signal. The voicing signal was detected by a

system beginning with a contact microphone. The contact

microphone was a unidirectional microphone from a hearing

aid. Since the contact microphone was unidirectional, it

generated a signal only during vocalization and did not

respond to environmental noise. The contact microphone was

held in place against the skin over one plate of the thyroid

lamina by an elastic band that went around the neck and

attached to itself by velcro strips at both ends. The

signal was amplified by a 5x AC amplifier and directed to a










second channel on the Visicorder, where it was simulta-

neously recorded with the air pressure signal.

Acoustic signal. The acoustic signal was detected by a

system beginning with a Quest 1.125 inch PZT ceramic omni-

directinal microphone at a mouth to microphone distance of

28.3 cm. The signal from the microphone passed through a

Quest model 215 sound level meter. This signal was then

amplified and recorded half track on an Akai GX-77 tape

recorder at a tape speed of 19 cm per second. The recorded

signal was directed through a rectifier-integrator circuit.

Then the speech signal envelope was processed through an A/D

converter and sent to a PDP-11/23 computer. The speech

signal envelope was sampled at a rate of 50 Hz, then

processed and analyzed.

Calibration. All equipment was calibrated before and

after each session. The intraoral air pressure system was

calibrated using a U-tube manometer. One inch increments of

pressure were induced into the system and the detected

changes in the fluid of the U-tube manometer caused by this

pressure were recorded in centimeters of water (cmH20) and

checked against previous recordings for reliability. A 1000

Hz tone at 110 dB SPL (re 0.0002 microbar) generated by a

Quest C-12 piston phone set over the microphone was recorded

at the beginning of each taping session to calibrate the

intensity measurement system. In this study the voicing

signal was a relevant variable only for its absence or

presence and not for its amplitude. The contact microphone










was tested for functioning by noting the presence of a

signal on the oscillographic trace during voicing and no

signal at other times.

The Visicorder also was used to observe the presence of

appropriate movement for the two signals displayed by the

galvonometers. This was most relevant for the pressure

signal, since the pressure sensing tube was susceptible to

being occluded by saliva. If the pressure sensing tube

became occluded, the experimenter disconnected it from the

pressure transducer and forced air through the tube from the

end that had been connected to the transducer. In this

manner any saliva was ejected from the tube, which was then

reconnected and the procedures continued or repeated if

necessary.

Speech sample. The consonants of interest were /p/,

/b/, /t/, /d/, /s/, and /z/. These consonants were com-

bined with the vowel /a/ in a series of CV, VCV, and VC

syllables. These syllables were imbedded in the carrier

phrase "Speak __ again." If the subject voiced contin-

uously through the consonants /b/, /d/, and /z/, the

investigator would have difficulty defining the limits of

prevoicing. So "speak" was used as the initial word in the

carrier phrase to minimize the occurrences of continuous

voicing, since the final /k/ is a voiceless phoneme. The

utterances were said at comfortable intensity and frequency

levels.










The subject was directed to repeat each phrase five

times. Each phrase was produced on a separate breath to

avoid variability caused by speaking on a reduced volume of

air. The middle three of the five phrase productions were

averaged to give the mean production value. In addition,

the middle three utterances were compared in order to

determine the constancy of production of the independent

variables. Use of the middle three utterances and not the

initial and final ones controlled for the series effect.

Malecot (1966b) defined the series effect as the systemic

variation in multiphasic utterances with utterance initial

phrases exhibiting greater speech effort and utterances

final phrases exhibiting lesser speech effort than the

central portion of the utterance.

The set of consonants used provided examples of stop

consonants at the labial and alveolar positions and frica-

tive consonants at the alveolar position in an established

phonetic environment. Place of articulation is a signifi-

cant variable for indices of speech timing as demonstrated

for phoneme duration (Lehiste, 1972; Stathopoulos & Weismer,

1983; Umeda, 1977) and voice onset time (Klatt, 1975; Lisker

and Abramson, 1964, 1967; Zlatin, 1974). Significant

variables for phoneme duration include manner of articu-

lation (Lehiste, 1972; Umeda, 1977), intraoral air pressure

(Arkebauer et al., 1967; Black, 1950; Brown, 1979; Brown &

McGlone, 1969a, 1969b; Malecot, 1955; Netsell, 1969),

consonantal voicing (Brown, 1979; Lisker, 1957 Muller &










Brown, 1980; Sharf, 1962), and voice onset time (Flege,

1982; Klatt, 1957; Lisker, 1957; Lisker & Abramson, 1964,

1967). By measuring the indices at both positions and in

both manners at the alveolar position, possible differences

by age were determined.

The phonetic environment was designed to maximize the

phonetic stability of the test consonant environment. A

constant vowel controlled for nonrelevant consonant varia-

tion caused by vowel differences (Oller, 1973). In

addition, using a carrier phrase avoided the phonetic

variability caused by utterance initial or final placement

(Muller and Brown, 1980).

Listening Task

The speech samples used for the listening task were the

second and third productions of the phrase "Speak /aba/

again." The second and third repetitions of the phrase are

relatively stable productions, since these repetition are

neither at the beginning nor end of the phrase repetitions.

The speech samples were duplicated from an Akai GX-77

two-track tape recorder onto a Panasonic RX-F11 cassette

tape recorder. During the listening sessions, the Panasonic

tape recorder was used. The listening environment was

structured such that the speech samples were at least 75 dB

at the heads of the listeners, as measured on a Quest 215

sound level meter.










Procedures

Speaking Task

Subject selection. All subjects were volunteers, with

the younger group consisting of students from the University

of Florda and residents of the Gainesville community, and

the older group consisting of individuals belonging to sev-

eral Gainesville senior citizens organizations. All sub-

jects completed the procedures during a five month period.

During a preliminary session each subject had her

hearing screened at 35 dB SPL for the frequencies 500 Hz,

1000 Hz, and 2000 Hz. The hearing screening task was first

in order to encourage participation. If she successfully

passed the hearing screening, she then completed the

questionnaire (Appendix A). If the potential subject met

the criteria specified by the questionnaire, then she read

the first paragraph of the "Rainbow Passage" (Fairbanks,

1954). If her articulation was within normal limits,

she was scheduled for an experimental session.

Preliminary procedures. When each subject arrived for

the experimental session, she was seated in an IAC booth.

The contact microphone was placed on the skin over one plate

of the thyroid lamina and kept in place by an elastic strap

with velcro at the ends that was positioned around the

subject's neck.

The acoustic microphone was positioned at a constant

microphone to mouth distance of 28.3 cm and at an angle of

25 degrees to the left of the mouth, relative to the front










of the face. The angle of the microphone and mouth to

microphone distance were maintained by having the subjects

place the front of their chin midway between their lower lip

and the bottom of their chin against a preset wooden scale.

Every subject was directed to keep her chin in contact with

the wooden scale.

Intensity procedures. The subject was directed to

produce the vowel /a/ three times for five seconds each at a

comfortable loudness level. For this task the sound level

meter was set at the dB level that most closely approx-

imates a 0 VU reading. Then she was asked to repeat the

vowel /a/ for five seconds at her maximum loudness level

three times. Again, the sound level meter was set using the

dB level that most closely approximates a 0 VU reading.

Each time she repeated the vowel /a/, the experimenter

urged her to produce it louder than she had the previous

time. Then the subject was asked to produce the vowel /a/

for five seconds at her minimum loudness level three times.

The sound level meter was again set to most closely

approximate a 0 VU reading. Each time she repeated the

vowel /a/, the experimenter encouraged her to produce it at

a softer level than the previous time. The maximum and

minimum loudness level productions were repeated three times

each so that the subjects were able to overcome normal

inhibitions against speaking at the limits of their dynamic

range.










The maximum volume task may be considered to be

subjective; however, it seemed that by encouraging the

subjects throughout the task, the loudest possible vocal-

ization samples were at least attempted. This task preceded

the timing and intraoral air pressure tasks so that the

voice was least fatigued when attempting the maximum

loudness task.

Timing and intraoral pressure procedures. For this

task, the subject had the pressure sensing tube positioned

in her mouth. Once the tube was correctly positioned, she

was directed to say a series of CV, VCV, and VC syllables

using the bilabial and alveolar stop and alveolar fricative

consonants /p/, /b/, /t/, /d/, /s/, /z/ and vowel /a/ for a

total of 18 test syllables. These syllables were inbedded

in the carrier phrase "Speak again." The subject was

instructed to repeat the utterances at comfortable frequency

and intensity levels. Each utterance was repeated until it

was judged by the experimenter to be produced at a comfort-

able level. Then, the subject was directed to repeat each

phrase five times, with each phrase production on a separate

breath.

Listening Tasks

Preliminary procedures. The 50 recordings were

duplicated and the second and third productions of "Speak

/aba/ again" were extracted. Each speaker was presented

twice in random sequence on the 100-item experimental tape.

Each item on the experimental tape included the item number,










followed by a one second pause, which was followed by the

experimental phrase, which was followed by a five second

pause. The experimental tape was played over a loudspeaker

to a group of listeners in a quiet room. Seating for all

listeners was adjusted to provide at least a 75 dB sound

pressure level at the head of each listener. These inten-

sity levels were calibrated before each listening session

using a Quest 215 sound level meter.

Experimental procedures. A multiple-choice rhyme-type

speech discrimination screening test (Griffiths, 1967) was

administered to all subjects at the beginning of each

listening session. To exhibit adequate listening skill, the

older subjects had to achieve a discrimination score of 84%

or better and the younger subjects had to achieve a

discrimination score of 97% or better.

After the speech discrimination test, the listeners

were informed that they were about to hear a tape of voices,

and that they were to estimate the age of each speaker.

Then, the listeners received a response sheet (Appendix C)

on which to write their age estimates. Once all the

listeners had their response sheets, they were told that the

voices they were about to hear came from two groups of

speakers, one young and one old. The listeners were

instructed to make the best estimate that they could as to

the age of the speaker for each voice sample. Additionally,

the listeners were told that the speech samples could be








62

repeated in order for them to make the best possible estima-

tion of speaker age. Five example items were provided at

the beginning of the experimental tape so that the listeners

could adapt to the task.

Analysis

Signal Analysis

Measurement of the peak intraoral air pressure and the

indices of speech timing, phoneme duration and voice onset

time, was accomplished by marking the oscillographic trace.

Vocal intensity was measured by a computer program (Hicks,

1980). Schematic examples of the oscillographic signal

and the points of measurement are depicted in Figure 1

(page 50).

Phoneme duration. Consonant duration (figure 1) was

determined from the point where the intraoral air pressure

trace departed from baseline (point a) until the drop in the

pressure tracing indicating the articulatory release of the

consonant (point b). The departure of the intraoral air

pressure signal from baseline (point a) indicated the moment

of articulatory closure, and the sudden drop in intraoral

air pressure (point b) indicated the moment of articulatory

release. Vowel duration was the time elapsed from the onset

of oscillation of the voicing trace (point c) until either

the final glottal pulse registered by the throat microphone

(point d) or the departure of the intraoral pressure tracing

from baseline for the following phoneme.










Voice onset time. Voice onset time (figure 1) was

defined as the time elapsed from the sudden drop of the

intraoral pressure trace indicating the articulatory release

of the consonant (point b) to the onset of oscillation of

the voicing signal (point c).

Intraoral air pressure. Peak intraoral air pressure

(figure 1) was indicated by the point of maximum departure

(point e) from baseline (point f) of the intraoral pressure

trace.

Vocal intensity. Vocal intensity was analyzed using

a computer software package developed by Hicks (1980). The

analysis procedure involved directing the taped speech signal

through a rectifier-integrator circuit. Then the speech

signal envelope was processed through an A/D converter and

sent to a PDP-11/23 computer. The speech signal envelope

was sampled at a rate of 50 Hz, and then processed and

analyzed. The printout from this program provided the

following information: A) mean intensity, B) standard

deviation, C) intensity distribution in two forms: 1) table

and 2) histogram (Figure 3). Information from the computer

printout was then converted to absolute intensity values by

determining the relationship between the intensity value of

the calibration tone generated by the piston phone and the

level at which the sound level meter had been set during the

initial recording. This procedure, which is depicted at

Figure 3 part c, converted the constant voltage output of

the sound level meter back to the original decibel values.














a. DISTRIBUTION TABLE
dB # %

65 5 1.94
66 32 12.40
67 25 9.69
68 31 12.02
69 19 7.36
70 20 7.75
71 52 20.16
72 56 21.71
73 17 6.59
74 1 0.39


c. sound level meter
setting = 110 dB
calibration tone = 74 dB
dB in distribution table
65 = 101
66 = 102
67 = 103
68 = 104
69 = 105
70 = 106
71 = 107
72 = 108
73 = 109
74 = 110


b. HISTROGRAM


**
**
**
**
**
**
**
**
***
* ***
* **
*** **
*** ***

*** ****


dB 5 5 6 6 7 7 8 8 9 9
0 5 0 5 0 5 0 5 0 5





Figure 3. Vocal intensity information was presented in a
distribution table (a) and a histogram (b) by the computer.
Conversion from the constant voltage level of the sound
level meter involved knowing the setting of the sound level
meter and intensity of the calibration tone (c).








65

Constancy of phoneme production. Constancy of phoneme

production across repetitions was analyzed for the middle

three productions of the test syllables. This analysis

involved comparing the standard deviations of the phoneme

durations, voice onset times, peak intraoral air pressure,

and vocal intensity using the F-max test for homogeneity of

variance (Winer, 1971).

Reliability

For the speaking tasks, both intra- and interjudge

reliability was determined. Random selections of 30% of the

tracings from the Visicorder were remeasured by the princi-

pal investigator to determine intrajudge reliability.

Similarly, random selections of 33% of the tracings were

measured by a second investigator to determine interjudge

reliability. Intrajudge reliability was 98% and interjudge

reliability was 97%. Ten percent of the intensity produc-

tions were analyzed twice using the computer program; inter-

run reliability was 96%. In addition, 10% of the intensity

productions were measured using a Bruel & Kjaer Graphic

Level Recorder. When the intensity levels measured from the

level recorder tracings were compared with those from the

computer printouts, the reliability between the two machines

was 92%. Lower reliability figures for this procedure may

be because of different sampling rates. The computer pro-

gram sampled the intensity productions at 50 Hz, while the

sampling of the level recorder tracings was at 10 Hz.












For the listening task, intrajudge reliability was

determined by correlating each of the judges first and

second age estimates for each of the speakers. This corre-

lation showed how consistent each of the judges was in

making age estimations.

Statistical Analysis

Independent variables in this study were a) the age

group of the speaker: young (20 to 35 years) and old (75

years and older); b) the consonants: stops /p/, /b/, /t/,

and /d/ and fricatives /s/ and /z/; c) the word place: word

initial, word medial, and word final; d) the vocal effort

level: comfortable, maximum, and minimum; and e) the age

group of the listener: young (20 to 35 years) and old (75

years and older). Dependent variables for the speaking

tasks of this study were 1) peak intraoral air pressure, 2)

consonant duration, 3) vowel duration, 4) voice onset time,

and 5) vocal intensity. The dependent variable for the

listening task was the estimated age of the speakers.

The primary method of statistical analysis for the

speaking tasks was analysis of variance (ANOVA). A 2 x 6 x

3 ANOVA was conducted for peak intraoral air pressure,

consonant duration, vowel duration, and voice onset time. A

2 x 3 ANOVA was conducted for vocal intensity. All ANOVAs

were performed with an alpha level of p=.05. Any signifi-

cant findings were explored pairwise using the Tukey LSD

method (Winer, 1971). Constancy of the productions within












speakers was tested using an F-max test for the homogeneity

of variances (Winer, 1971).

The primary method of statistical analysis for the

listening task was the Pearson product-moment correla-

tion. The mean age estimation by the listeners were

calculated for each speech sample. These means were

correlated with the chronological age of each speaker.

Previous researchers consistently have found high corre-

lations, r=.76 to r=.93, between perceived speaker age and

chronological age (Hartman, 1979; Hartman & Danhauer, 1976;

Horii & W. Ryan, 1981; E. Ryan & Capadano, 1978; W. Ryan &

Burk, 1974; Shipp & Hollien, 1969).

















CHAPTER IV
RESULTS

Introduction

The purpose of this study was to investigate the

possible presence of age-related physiological differences

between the speech of two groups of adult females. These

differences were investigated for the variables of (1)

speech timing, (2) intraoral air pressure, and (3) vocal

intensity.

Speech timing and intraoral air pressure recordings

were obtained from a system that began with (1) a throat

microphone and (2) a sensing tube attached to a pressure

transducer. These signals were amplified and displayed as

tracings from two channels on the print out of an oscillo-

graphic recorder. Tracings on these print outs were

measured to obtain information on the dependent variables

(1) peak intraoral air pressure, (2) consonant duration, (3)

vowel duration, and (4) voice onset time.

Vocal intensity data were obtained through a system

that included a condenser microphone, a sound level meter,

and an audio tape recorder. The recorded signals were

directed through a rectifier-integrator circuit, an A/D

converter at a sampling rate of 50 Hz, and a PDP-11/23

computer. The output from the computer was converted

68











from the sound level meter constant voltage levels to the

decibel levels of the original signal.

Perceptual data were obtained by playing short utter-

ances from each speaker to two groups of listeners, one

group age matched with the younger speakers and the with the

older speakers. The listeners recorded their estimation of

the age of each speaker that they heard.

Research Findings

All the dependent variables were analyzed for differ-

ences between the two age groups using ANOVA statistical

techniques. The variables of (1) peak intraoral air

pressure, (2) consonant duration, (3) vowel duration, and

(4) voice onset time were analyzed for the effect of the

consonants and, with the exception of voice onset time,

syllable position. When appropriate, ANOVAs of the

interactions of age group, consonant, and syllable position

were completed.

Intraoral Air Pressure

Peak intraoral air pressure was operationally defined

for this study as the distance from the baseline of the

pressure trace on the oscillograph to the greatest deflec-

tion from that baseline. Variations in peak intraoral

pressure magnitudes were analyzed for both age groups by

consonant and by syllable position. The comparisons were

completed both within and between the age groups.








70

Significant differences in peak intraoral air pressure

were found between the two age groups (Table 1). Signifi-

cant differences were found for the interactions of (1) age

with consonant and (2) age, consonant, and syllable posi-

tion. The interactions of age and syllable position and did

not exhibit significant differences between the two age

groups.

Consonants. Both age groups exhibited greater peak

intraoral air pressure values for the voiceless consonants

/p/, /t/, and /s/ in comparison to the voiced consonants

/b/, /d/, and /z/. Within group comparisons, using Tukey's

Studentized Range (Winer, 1971), indicated that the peak

intraoral pressure values from both groups of speakers had

significant differences between /p/, /t/, and /s/ and the

voiced stops, /b/ and /d/ (Table 2). Intraoral pressure

values for /z/ did not differ significantly from the

voiceless consonants for the older speakers.

Between group comparisons of peak intraoral pressure

magnitudes revealed significantly greater intraoral pressure

values among the older speakers than among the younger

speakers for the consonants /p/, /t/, /s/, and /z/ (figure

6). The two voiced stop consonants, /b/ and /d/, exhibited

no significant differences in peak intraoral pressure

between the two age groups.











Table 1. Within and between age group ANOVAs of intraoral
air pressure for the experimental conditions.


Condition
BETWEEN GROUPS
Age


df SS F p


Error
Consonant
Age x Cons.
Error
Syllable Position
Age x Syl. Position
Cons. x Syl. Position
Age x Cons. x Syl. Pos.
Error
WITHIN GROUPS
OLDER SUBJECTS
Consonant
Error
Syllable
Consonant x Syllable
Error
YOUNGER SUBJECTS
Consonant
Error
Syllable
Consonant x Syllable
Error


193.20
1974.02
1477.89
188.54
961.24
269.60
6.92
237.84
55.22
877.31


1324.95
4899.21
153.84
102.64
432.91

344.32
232.94
151.80
139.60
993.70


4.70

73.80
9.41

80.51
2.07
15.78
3.66


0.0352*

0.0001*
0.0001*

0.0001*
0.1275
0.0001*
0.0002*


43.62 0.0001*

42.29 0.0001*
5.64 0.0001*


35.48

55.47
13.86


0.0001*

0.0001*
0.0001*


* indicates a significant difference within the condition


Table 2. Within age group comparisons of intraoral air
pressure (PIO) levels for each consonant.

Mean PIO Tukey
Consonant in cmH20 Grouping
OLDER SUBJECTS
/p/ 8.42 A
/s/ 8.21 A
/t/ 7.42 A
/z/ 7.10 A
/b/ 4.38 B
/d/ 4.15 B
YOUNGER SUBJECTS
/s/ 6.59 A
/p/ 6.53 A
/t/ 6.28 A
/z/ 5.29 B
/b/ 4.74 B C
/d/ 4.39 C

Means with the same letter under Tukey Grouping do not
differ significantly








72

The between age group difference in peak intraoral air

pressure was examined for the effect of dental status. The

women who wore dentures produced consonants with signifi-

cantly greater intraoral air pressure than either the

younger or older women with natural teeth, the dentate

speakers (Table 3). No significant differences were found

between the younger and older dentate women.

Syllable position. Within age group comparisons of

the peak intraoral pressure values revealed significant

differences by syllable position for the consonants /t/ and

/d/ among the older subjects, and /t/, /d/, and /b/ among

the younger subjects (Table 4). When significant differ-

ences by syllable position occurred, syllable initial

consonants exhibited greater peak intraoral air pressure

values than did syllable final consonants.

The three way interaction of age, consonant, and

syllable position also was significant for peak intraoral

air pressure (Table 1). When the data were more closely

examined (Table 5), the consonants /t/, /d/, and /b/ again

differed from the other test consonants. While the other

test consonants consistently exhibited significant differ-

ences between the two age groups, /t/, /d/, and /b/

exhibited individual patterns. For the /t/ productions, the

CV and VCV syllables exhibited significant differences

between the age groups, while the VC syllables did not. For

the /d/ productions, the CV syllables exhibited significant

differences between the age groups, while the VCV and VC











syllables did not. Finally, for the /b/ productions, none

of the syllable positions exhibited significant differences

between the two age groups.
















9 Older
9Speakers
8 Younger
8 Speakers

7
0
6

E
u 5

4
O
EL 3

2

1

0


/p/ /b/ It/ /d/ Is/ /z/

consonants


Figure 4.


Between group comparisons of peak intraoral
pressure (PIO) by consonant.










Table 3. Comparison of peak intraoral air pressure (PIO) by
age group and dental status.


Voiceless Cons. Voiced Cons.
Mean PIO Mean PIO
Subjects n in cmH20 Tukey in cmH20 Tukey

DENTATE
Younger 25 6.47 A 4.80 A
Older 10 7.02 A 4.21 A

DENTURE WEARING
Older 15 8.69 B 5.83 B

different letter under Tukey Group indicates a significant
difference




Table 4. Within age group comaprisons of peak intraoral air
pressure (PIO) by syllable position.


Older Subjects
Mean PIO Tukey
in cmH20 Group
8.76 A
8.30 A
8.20 A


4.71
4.53
3.90

8.74
8.11
5.41

5.16
4.31
2.97

8.78
8.41
7.43

7.22
7.15
6.94


Younger Subjects
Mean PIO Tukey
in cmH20 Group
6.39 A
6.75 A
6.47 A


5.92
4.18
4.11

7.08
6.65
4.98

6.68
3.78
2.71

7.08
6.59
6.10

5.42
5.23
5.20


Different letters
difference


under Tukey group represents a significant


Syllable
/pa/
/apa/
/a p/

/ba/
/a ba/
/ab/


/ta/
/a t /
/att/

/da/
/ad a/
/a d/

/s a/
/as a/
/as/

/za/
/az a/
/az/










Table 5. Between age
pressure by


Dependent


Dependent
Variable

/pa/

/a pa/

/a p/


/ba/

/aba/

/ab/


/ta/

/ata/

/at/


/da/

/a da/

/ad/


/sa/

/a sa/

/a s/

/za/

/aza/

/az/


Source

Age
Error
Age
Error
Age
Error

Age
Error
Age
Error
Age
Error

Age
Error
Age
Error
Age
Error

Age
Error
Age
Error
Age
Error

Age
Error
Age
Error
Age

Age
Error
Age
Error
Age
Error


group comparisons of intraoral air
consonant at each syllable position.


SS

114.109
960.832
382.484
1287.087
257.425
1634.491

84.213
1463.605
18.692
857.093
4.650
951.910

231.255
1509.000
179.642
1745.090
40.135
2488.357

148.718
1447.762
31.576
1606.351
8.276
722.780

274.687
1400.597
319.741
1443.117
165.056

378.175
1222.905
265.327
1188.827
160.064
1229.816


F

13.57

13.37

7.09


2.59

0.98

0.22


6.90

4.61

0.73


4.62

0.88

0.52


8.83

9.97

4.28

13.92

10.04

5.86


* Indicates a significant difference between the age groups


p

0.0006*

0.0006*

0.0107*


0.1145

0.3272

0.6414


0.0118*

0.0370*

0.3988


0.0370*

0.3520

0.4766


0.0048*

0.0028*

0.0443*

0.0005*

0.0027*

0.0196*










Consonant Duration

Consonant duration was operationally defined as the

difference between the onset of the air pressure pulse rise

(consonant closure) on the oscillograph trace to the sudden

drop of pressure (consonant release). Variations in

consonant duration were analyzed for both age groups by

consonant and by syllable position. The comparisons were

completed both within and between the age groups.

Significant main effects were found for each of the

three experimental conditions: age group, consonant, and

syllable position (Table 6). Significant interactions also

were found among the consonants by syllable positions.

Within group comparisons (Table 6) revealed that for

both the older and younger subjects, significant differences

were found for the main effects of consonant and syllable

position. Significant interaction effects also were found

for both age groups for the consonant by syllable

interaction.

Consonants. The voiceless consonants were produced

with greater consonant duration than the voiced consonants

for both age groups (Table 7). The older speakers exhibited

greater consonant durations than the younger speakers for

both the voiced and voiceless consonants. The data in Table

6 reveal that consonants produced by the younger subjects

exhibited significant differences for each cognate pair: /s/

greater than /z/, /p/ greater than /b/, and /t/ greater than

/d/. The older subjects, however, exhibited significant











differences only for the alveolar fricatives, /s/ and /z/,

and bilabial stops, /p/ and /b/.


















Table 6. Between and within group ANOVAs for consonant
duration for the experimental conditions.


Condition
BETWEEN GROUPS
Age
Error
Consonant
Age x Cons.
Error
Syllable Position
Age x Syl. Pos.
Cons. x Syl. Position
Age x Cons. x Syl. Pos.
Error

WITHIN GROUPS
OLDER SUBJECTS
Consonant
Error
Syllable
Consonant x Syllable
Error
YOUNGER SUBJECTS
Consonant
Error
Syllable
Consonant x Syllable
Error


df SS F p


0.077
0.237
0.256
0.004
0.442
0.089
0.004
0.061
0.005
0.399



0.139
0.144
0.032
0.039
0.201

0.121
0.052
0.055
0.039
0.142


50.36
14.52
33.41
0.55

58.16
2.92
8.94
0.80


0.0001*
0.0004*
0.0001*
0.7353

0.0001*
0.0548
0.0001*
0.6145


23.15 0.0001*

18.95 0.0001*
4.69 0.0001*


56.16

54.87
7.84


0.0001*

0.0001*
0.0001*


* indicates a significant difference within the condition










Table 7. Consonant durations (CD) for each consonant by
age group.


Mean CD Tukey
Consonant in msec Grouping
OLDER SUBJECTS
/s/ 144 A
/p/ 126 B
/z/ 115 BC
/b/ 106 C
/t/ 104 C D
/d/ 88 D

YOUNGER SUBJECTS
/s/ 125 A
/p/ 101 B
/z/ 97 B
/t/ 92 BC
/b/ 83 C
/d/ 72 D

Means with the same letter under Tukey Grouping are not
significantly different


Significant differences exist between the age groups

for all of the consonant durations, except for the consonant

/t/ (Figure 5). For the other test consonants, the older

subjects exhibited significantly greater consonant durations

than did the younger subjects.

Syllable position. The within age group comparisons

of consonant durations by syllable position revealed similar

patterns of significant differences for the younger and

older groups (Table 8). For most of the consonants, the

CV syllables exhibited significantly longer consonant dura-

tions than the VC syllables. The consonant /t/ was the

exception to this pattern, exhibiting insignificant differ-

ences in consonant duration among the three syllable

positions.


















Older
Speakers

Younger
Speakers


/pl /b/ It/ Id/ /s/ /zl


consonants




Figure 5. Between age group comparisons for consonant
duration (CD) by consonant.










Table 8. Within age group comparisons of consonant
duration by syllable position.


Older Subjects
Mean CD Tukey
in msec Group
0.143 A
0.122 A B
0.114 B


Syllable
/pa/
/apa/
/ap/

/ba/
/aba/
/ab/

/ta/
/ata/
/at/


Younger Subjects
Mean CD Tukey
in msec Group
0.092 A
0.100 A B
0.110 B


0.110
0.069
0.068

0.101
0.087
0.085

0.103
0.057
0.056

0.139
0.119
0.117

0.116
0.092
0.083


Different letters under Tukey
difference among the syllable


Group indicate significant
positions


0.127
0.101
0.090

0.113
0.104
0.095

0.103
0.084
0.078

0.162
0.138
0.131

0.131
0.098
0.112


/d a/
/ada/
/ad/

/s /
/as a/
/as/

/za/
/aza /
/az/










Vowel Duration

Vowel duration was operationally defined as the differ-

ence between the onset of the oscillation of the voicing

trace (voicing onset) on the oscillograph print out and the

return of the voicing trace to baseline (voicing offset).

Variability in vowel duration was analyzed for both age

groups by consonant and by syllable position. The compari-

sons were completed both within and between the age groups.

Vowel duration variability was examined within and

between the two age groups for each consonant context in the

VCV and VC syllable conditions. Table 9 indicates that

significant differences were found between the age groups

for each of the three experimental conditions: age group,

consonant, and syllable position. In addition, significant

interactions were found (1) between the age groups by

consonant, (2) between the age groups by syllable position,

and (3) among the consonant by syllable position. However,

no significant three way interaction was found for vowel

duration among the three experimental conditions. The older

speakers exhibited greater vowel durations in all consonant

conditions (Figure 6).

Within age group comparisons indicated that both age

groups exhibited significant effects for the experimental

conditions of consonant, syllable position, and the

interaction of consonant and syllable position (Table 9).











Table 9. Between and within ANOVAs for vowel duration (VD)
for the experimental conditions.


Condition


df SS F


BETWEEN GROUPS
Age
Error
Consonant
Age x Cons.
Error
Syllable position
Age x Syl.
Cons. x Syl.
Age x Cons. x Syl.
Error

WITHIN GROUPS
OLDER SUBJECTS
Consonant
Error
Syllable
Consonant x Syllable
Error

YOUNGER SUBJECTS
Consonant
Error
Syllable
Consonant x Syllable
Error


0.303
0.507
0.419
0.029
0.344
0.457
0.015
0.055
0.009
0.379



0.312
0.234
0.324
0.044
0.130


0.136
0.109
0.145
0.021
0.071


28.77

57.76
4.00

342.04
10.96
8.22
1.29


0.0001*

0.0001*
0.0017*

0.0001*
0.0011*
0.0001*
0.2700


31.66 0.0001*


295.23
8.04



29.85

237.56
7.20


0.0001*
0.0001*



0.0001*

0.0001*
0.0010*


experimental


* indicates a significant difference within the
condition













SOlder
Speakers
Younger
300 1Speakers
300


250


200


150

E
C 100


50




/p/ /b/ It/ /d/ /s/ /z/

Consonant Context


Figure 6. Between age group comparisons of vowel durations
(VD) by consonant context.


Consonants. The within group comparisons of vowel

duration for each consonant context are displayed in Table

10. For both age groups, the vowel durations were greatest

in the alveolar fricative context and least in the bilabial

stop context. The vowel durations in the context of voiced

consonants were significantly greater than those in the

context of voiceless consonants (Table 10). Additionally,

the data in Table 10 demonstrate that the older speakers

exhibited longer vowel durations for both the voiced and

voiceless consonant contexts.










Table 10. Within group comparisons of vowel duration (VD)
for each consonant by age group.


Mean VD
Consonant in msec
OLDER SUBJECTS
/z/ 275
/d/ 268
/b/ 246
/s/ 240
/t/ 208
/p/ 183

YOUNGER SUBJECTS
/z/ 227
/d/ 207
/b/ 191
/s/ 190
/t/ 173
/p/ 160

Consonants sharing the same
not differ significantly


Tukey
Grouping

A
A B


C D
D

letter under Tukey Grouping do


Syllable Position. Within age group comparisons

revealed that both the older and younger speakers exhibited

greater vowel durations in the VC condition than they did

for the VCV condition (Figure 7). Thus, while the numeric

values differed for the vowel durations between the two age

groups, they exhibited the same pattern of vowel duration

differences between the syllable conditions.

Between age group comparisons of vowel duration

revealed significant differences between the two groups by

syllable position and by consonant (Table 11). The older

subjects consistently exhibited significantly greater vowel

durations when compared to the younger speakers. Differ-

ences in vowel duration were found for both syllable

positions in every consonant context.




















250


0200

E
.E 150


100


50


Younger
Speakers

Older
Speakers


VC
Syllables


VCV
Syllables


Figure 7. Within and between age group comparisons of
vowel duration (VD) by syllable position.











Table 11. Between age group and between
comparisons of vowel duration


syllable position
(VD) by consonant.


Consonant Source

/p/ Age
Error
Syl. Pos.
Error


Age
Error
Syl. Pos.
Error

Age
Error
Syl. Pos.
Error

Age
Error
Syl. Pos.
Error

Age
Error
Syl. Pos.
Error

Age
Error
Syl Pos.
Error


df SS F p


0.013
0.087
0.015
0.026

0.075
0.130
0.096
0.055

0.029
0.113
0.036
0.055

0.094
0.168
0.171
0.090

0.066
0.183
0.058
0.075

0.056
0.171
0.135
0.078


7.44 0.0089*

26.11 0.0001*


27.51

82.74


0.0001*

0.0001*


12.24 0.0010*

31.27 0.0001*


26.84 0.0001*

88.94 0.0001*


17.37 0.0001*

37.29 0.0001*


15.47 0.0003*

81.76 0.0001*


* indicates a significant difference in vowel duration for
the consonant under the stated condition











Voice Onset Time

Voice onset time was operationally defined as the

difference between the sudden drop of the pressure pulse

trace on the oscillograph print out (consonant release) and

the onset of oscillation of the voicing trace (vowel onset).

Variability in voice onset time was analyzed for both age

groups by consonant in the CV syllable position. The

comparisons were completed both within and between the age

groups.

Voice onset time varied significantly between the age

groups, among the consonants, and by consonant between the

age groups (Table 12). Within age group analyses revealed

significant differences among the consonants in both the

older and younger age groups.



Table 12. Between and within group ANOVAs for voice onset
time for the experimental conditions.


Condition df SS F p

BETWEEN GROUPS
Age 1 0.043 19.36 0.0001*
Error 48 0.105
Consonant 5 0.517 95.31 0.0001*
Age x Consonant 5 0.031 5.77 0.0002*
Error 239 0.260

WITHIN GROUPS
OLDER SUBJECTS
Consonants 5 0.293 38.04 0.0001*
Error 119 0.183
YOUNGER SUBJECTS
Consonants 5 0.259 34.25 0.0001*
Error 120 0.182


* indicates a significant
condition


difference within the


experimental








88

For both age groups, the voiceless stop consonants /p/

and /t/ had significantly greater voice onset time values

than the voiced consonants /z/, /b/, and /d/ (Table 13).

For the older speakers, the consonants /p/ and /t/ had

significantly longer voice onset times than /s/, and /s/ had

significantly longer voice onset times than /b/, /d/, and

/z/. For the younger speakers, the voice onset times of

/s/, /d/, and /b/ did not differ significantly. However,

the /z/ exhibited significantly shorter voice onset times

than the other voiced consonants produced by the younger

subjects.





Table 13. Within age group comparisons of voice onset time
(VOT) by consonant.


Mea
Consonant in

OLDER SUBJECTS
/p/
/t/
/s/
/b/
/d/
/z/

YOUNGER SUBJECTS
/p/
/t/
/s/
/b/
/d/
/z/

Consonants with the
differ significantly


n VOT
msec


Tukey
Grouping


6 B
1 B
56

same letter under Tukey


C

Grouping do not










Between age group comparisons of voice onset time

revealed that the younger women produced significantly

longer voice onset times than the older women for the

consonants /p/, /b/, /t/, /d/, and /s/ (Figure 8). Only

the consonant /z/ did not exhibit voice onset times that

differed significantly between the two groups.


/p/ /b/ It/ Id/
Consonant


/S/ /z/


Figure 8. Between age group comparisons of voice onset time
(VOT) by consonant.








90

A factor that may have influenced the voice onset time

data was the occurrence of continuous voicing. Continuous

voicing indicated that a speaker did not discontinue voicing

during the /k/ sound of the word 'speak' in the carrier

phrase, but voiced the vowel /i/ into the next syllable.

This phenomenon was more prevalent among the older speakers,

occurring 56 times on 29 different consonants in comparison

to 38 occurrences on 14 different consonants among the

younger group.

For measurement purposes, the voice onset time for the

continuously voiced consonants was labeled as prevoiced with

a magnitude equal to the value of the consonant duration.

These voice onset times were operationally defined as the

difference between the consonant closure indicated on the

pressure trace and the onset of the vowel on the voicing

trace.

Vocal Intensity

Intensity levels of the speakers' utterances of

sustained /a/ were recorded at three effort levels: minimum,

comfortable, and maximum. The intensity data were analyzed

for significant differences with a 2 x 3 ANOVA. Variations

in intensity level were analyzed for both age groups by

effort level.

Significant differences in vocal intensity were found

for the main effect of effort level and the interaction of

effort level and age group (Table 14). No significant










differences in vocal intensity were found for the main

effect of age group.

Table 14. Between and within group ANOVAs for vocal
intensity for the experimental conditions.


Condition df SS F p
Age 1 15.59 0.52 0.476
Error 48 1444.00
Effort level 2 60776.88 1333.36 0.0001*
Age x Effort level 2 1631.64 35.80 0.0001*
Error 95 2165.13


*indicates a significant difference for this condition


For both age groups the vocal intensity varied directly

with effort level; the greatest intensities were generated

during the maximum efforts and the least intensities were

generated during the minimum efforts. The interaction of

effort level with the age groups was significant for the

maximum level and the minimum level, but not for the

comfortable level (Figure 9). The data in Figure 9 indicate

that the younger speakers exhibited greater maximum effort

intensity levels and lower minimum effort intensity levels

when compared to the older speakers.



















Older
Speakers

Younger
Speakers


Maximum Conversation
Effort Effort


Minimum
Effort


Figure 9. Between age group comparisons of vocal intensity
(SPL) by effort level.











Variability of Speech Production

The variability of the repeated utterances was analyzed

between the groups for the production of the dependent

variables (1) peak intraoral air pressure, (2) consonant

duration, (3) vowel duration, (4) voice onset time, and (5)

vocal intensity. The F-max test for homogeniety of

variance was used to compare the variability between the two

age groups. Significant differences in variability were

found between the two age groups for all the dependent

variables (Table 15). Since no significant age effects were

exhibited for the vocal intensity task, variability was

analyzed between age groups by effort level. This revealed

significantly different levels of variability between the

two age groups for the minimum effort level only.

Table 15. Between age group comparisons of variability by
dependent variable.


Dependent
Variable Age Group df F P
Intraoral Air Pressure Older 446 1.88 0.0001*
Younger 448
Consonant Duration Older 446 1.72 0.0001*
Younger 448
Vowel Duration Older 296 2.01 0.0001*
Younger 297
Voice Onset Time Older 145 2.66 0.0001*
Younger 147
Intensity
Minimum Older 74 2.91 0.011*
Younger 74
Comfortable Older 74 1.12 0.782
Younger 73
Maximum Older 74 1.34 0.477
Younger 73

*indicates a significant difference between the age groups