the mit press the mit encyclopedia of communication disorders oct 2003

Introduction ix Acknowledgments xi Part I: Voice 1 Acoustic Assessment of Voice 3 Aerodynamic Assessment of Vocal Function 7 Alaryngeal Voice and Speech Rehabilitation 10 Anatomy of the

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The MIT Encyclopedia of Communication Disorders

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The MIT Encyclopedia of Communication Disorders

Edited by Raymond D Kent

A Bradford BookThe MIT PressCambridge, Massachusetts

London, England

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All rights reserved No part of this book may be reproduced in any form by any electronic or mechanical means (including photocopying, recording, or information storage and retrieval) without permission in writing from the publisher.

This book was set in Times New Roman on 3B2 by Asco Typesetters, Hong Kong, and was printed and bound in the United States of America.

Library of Congress Cataloging-in-Publication Data

The MIT encyclopedia of communication disorders / edited by Raymond D Kent.

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Introduction ix

Acknowledgments xi

Part I: Voice 1

Acoustic Assessment of Voice 3

Aerodynamic Assessment of Vocal Function 7

Alaryngeal Voice and Speech Rehabilitation 10

Anatomy of the Human Larynx 13

Assessment of Functional Impact of Voice

Disorders 20

Electroglottographic Assessment of Voice 23

Functional Voice Disorders 27

Hypokinetic Laryngeal Movement Disorders 30

Infectious Diseases and Inﬂammatory Conditions of

the Larynx 32

Instrumental Assessment of Children’s Voice 35

Laryngeal Movement Disorders: Treatment with

Botulinum Toxin 38

Laryngeal Reinnervation Procedures 41

Laryngeal Trauma and Peripheral Structural

Ablations 45

Psychogenic Voice Disorders: Direct Therapy 49

The Singing Voice 51

Vocal Hygiene 54

Vocal Production System: Evolution 56

Vocalization, Neural Mechanisms of 59

Voice Acoustics 63

Voice Disorders in Children 67

Voice Disorders of Aging 72

Voice Production: Physics and Physiology 75

Voice Quality, Perceptual Evaluation of 78

Voice Rehabilitation After Conservation

Laryngectomy 80

Voice Therapy: Breathing Exercises 82

Voice Therapy: Holistic Techniques 85

Voice Therapy for Adults 88

Voice Therapy for Neurological Aging-Related Voice

Disorders 91

Voice Therapy for Professional Voice Users 95

Part II: Speech 99

Apraxia of Speech: Nature and Phenomenology 101

Apraxia of Speech: Treatment 104

Bilingualism, Speech Issues in 119

Developmental Apraxia of Speech 121

Laryngectomy 137Mental Retardation and Speech in Children 140Motor Speech Involvement in Children 142Mutism, Neurogenic 145

Orofacial Myofunctional Disorders in Children 147Phonetic Transcription of Children’s Speech 150Phonological Awareness Intervention for Children withExpressive Phonological Impairments 153

Phonological Errors, Residual 156Phonology: Clinical Issues in Serving Speakers ofAfrican-American Vernacular English 158Psychosocial Problems Associated with CommunicativeDisorders 161

Speech and Language Disorders in Children: Based Approaches 164

Computer-Speech and Language Issues in Children from Paciﬁc Backgrounds 167

Asian-Speech Assessment, Instrumental 169Speech Assessment in Children: Descriptive Linguistic

Speech Disorders in Children: Behavioral Approaches toRemediation 192

Speech Disorders in Children: Birth-Related RiskFactors 194

Speech Disorders in Children: Cross-Linguistic

Speech Disorders Secondary to Hearing ImpairmentAcquired in Adulthood 207

Speech Issues in Children from LatinoBackgrounds 210

Speech Sampling, Articulation Tests, and Intelligibility

in Children with Phonological Errors 213Speech Sampling, Articulation Tests, and Intelligibility

in Children with Residual Errors 215Speech Sound Disorders in Children: Description andClassiﬁcation 218

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Stuttering 220

Transsexualism and Sex Reassignment: Speech

Di¤erences 223

Ventilator-Supported Speech Production 226

Part III: Language 229

Aphasia, Primary Progressive 245

Aphasia: The Classical Syndromes 249

Aphasia, Wernicke’s 252

Aphasia Treatment: Computer-Aided

Rehabilitation 254

Aphasia Treatment: Pharmacological Approaches 257

Aphasia Treatment: Psychosocial Issues 260

Aphasic Syndromes: Connectionist Models 262

Aphasiology, Comparative 265

Argument Structure: Representation and

Processing 269

Attention and Language 272

Auditory-Motor Interaction in Speech and

Augmentative and Alternative Communication: General

Issues 277

Bilingualism and Language Impairment 279

Communication Disorders in Adults: Functional

Functional Brain Imaging 305

Inclusion Models for Children with Developmental

Language Disorders in Latino Children 321

Language Disorders in School-Age Children: Aspects of

Assessment 324

Language Disorders in School-Age Children:

Overview 326

Language Impairment and Reading Disability 329

Language Impairment in Children: Cross-Linguistic

Studies 331

Language in Children Who Stutter 333

Language of the Deaf: Acquisition of English 336

Language of the Deaf: Sign Language 339

Lingustic Aspects of Child Language Impairment—Prosody 344

Melodic Intonation Therapy 347Memory and Processing Capacity 349Mental Retardation 352

Morphosyntax and Syntax 354Otitis Media: E¤ects on Children’s Language 358Perseveration 361

Phonological Analysis of Language Disorders inAphasia 363

Phonology and Adult Aphasia 366Poverty: E¤ects on Language 369Pragmatics 372

Prelinguistic Communication Intervention for Childrenwith Developmental Disabilities 375

Preschool Language Intervention 378Prosodic Deﬁcits 381

Reversibility/Mapping Disorders 383Right Hemisphere Language and CommunicationFunctions in Adults 386

Right Hemisphere Language Disorders 388Segmentation of Spoken Language by Normal AdultListeners 392

Semantics 395Social Development and Language Impairment 398Speciﬁc Language Impairment in Children 402Syntactic Tree Pruning 405

Trace Deletion Hypothesis 407

Part IV: Hearing 411

Amplitude Compression in Hearing Aids 413Assessment of and Intervention with Children Who AreDeaf or Hard of Hearing 421

Audition in Children, Development of 424Auditory Brainstem Implant 427

Auditory Brainstem Response in Adults 429Auditory Neuropathy in Children 433Auditory Scene Analysis 437

Auditory Training 439Classroom Acoustics 442Clinical Decision Analysis 444Cochlear Implants 447Cochlear Implants in Adults: Candidacy 450Cochlear Implants in Children 454

Dichotic Listening 458Electrocochleography 461Electronystagmography 467Frequency Compression 471Functional Hearing Loss in Children 475Genetics and Craniofacial Anomalies 477Hearing Aid Fitting: Evaluation of Outcomes 480Hearing Aids: Prescriptive Fitting 482

Hearing Aids: Sound Quality 487Hearing Loss and the Masking-Level Di¤erence 489Hearing Loss and Teratogenic Drugs or Chemicals 493Hearing Loss Screening: The School-Age Child 495Hearing Protection Devices 497

Middle Ear Assessment in the Child 504

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Noise-Induced Hearing Loss 508

Otoacoustic Emissions 511

Otoacoustic Emissions in Children 515

Ototoxic Medications 518

Pediatric Audiology: The Test Battery Approach 520

Physiological Bases of Hearing 522

Pitch Perception 525

Presbyacusis 527

Pseudohypacusis 531

Pure-Tone Threshold Assessment 534

Speech Perception Indices 538

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The MIT Encyclopedia of Communication Disorders (MITECD) is a comprehensivevolume that presents essential information on communication sciences and disorders.The pertinent disorders are those that a¤ect the production and comprehension ofspoken language and include especially disorders of speech production and percep-tion, language expression, language comprehension, voice, and hearing Potentialreaders include clinical practitioners, students, and research specialists Relativelyfew comprehensive books of similar design and purpose exist, so MITECD standsnearly alone as a resource for anyone interested in the broad ﬁeld of communicationdisorders

MITECD is organized into the four broad categories of Voice, Speech, Language,and Hearing These categories represent the spectrum of topics that usually fall underthe rubric of communication disorders (also known as speech-language pathologyand audiology, among other names) For example, roughly these same categorieswere used by the National Institute on Deafness and Other Communication Dis-orders (NIDCD) in preparing its national strategic research plans over the past de-cade The Journal of Speech, Language, and Hearing Research, one of the mostcomprehensive and influential periodicals in the field, uses the editorial categories ofspeech, language, and hearing Although voice could be subsumed under speech, thetwo fields are large enough individually and su‰ciently distinct that a separation iswarranted Voice is internationally recognized as a clinical and research specialty,and it is represented by journals dedicated to its domain (e.g., the Journal of Voice).The use of these four categories achieves a major categorization of knowledge butavoids a narrow fragmentation of the field at large It is to be expected that theEncyclopedia would include cross-referencing within and across these four majorcategories After all, they are integrated in the definitively human behavior of lan-guage, and disorders of communication frequently have wide-ranging e¤ects oncommunication in its essential social, educational, and vocational roles

In designing the content and structure of MITECD, it was decided that each ofthese major categories should be further subdivided into Basic Science, Disorders(nature and assessment), and Clinical Management (intervention issues) Althoughthese categories are not always transparent in the entire collection of entries, theyguided the delineation of chapters and the selection of contributors These categoriesare deﬁned as follows:

Basic Science entries pertain to matters such as normal anatomy and physiology,physics, psychology and psychophysics, and linguistics These topics are thefoundation for clinical description and interpretation, covering basic principlesand terminology pertaining to the communication sciences Care was taken toavoid substantive overlap with previous MIT publications, especially the MITEncyclopedia of the Cognitive Sciences (MITECS)

The Disorders entries o¤er information on issues such as syndrome delineation,definition and characterization of specific disorders, and methods for the iden-tification and assessment of disorders As such, these chapters reflect contempo-rary nosology and nomenclature, as well as guidelines for clinical assessment anddiagnosis

The Clinical Management entries discuss various interventions including behavioral,pharmacological, surgical, and prosthetic (mechanical and electronic) There is ageneral, but not necessarily one-to-one, correspondence between chapters in theDisorders and Clinical Management categories For example, it is possible thatseveral types of disorder are related to one general chapter on clinical manage-ment It is certainly the case that di¤erent management strategies are preferred bydi¤erent clinicians The chapters avoid dogmatic statements regarding interven-tions of choice

Because the approach to communicative disorders can be quite di¤erent for dren and adults, a further cross-cutting division was made such that for many topics

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chil-separate chapters for children and adults are included Although some disorders thatare first diagnosed in childhood may persist in some form throughout adulthood (e.g,stuttering, specific language impairment, and hearing loss may be lifelong conditionsfor some individuals), many disorders can have an onset either in childhood or inadulthood and the timing of onset can have implications for both assessment andintervention For instance, when a child experiences a significant loss of hearing, thesensory deficit may greatly impair the learning of speech and language But when aloss of the same degree has an onset in adulthood, the problem is not in acquiringspeech and language, but rather in maintaining communication skills Certainly, it isoften true that an understanding of a given disorder has common features in both thedevelopmental and acquired forms, but commonality cannot be assumed as a generalcondition.

Many decisions were made during the preparation of this volume Some wereeasy, but others were not In the main, entries are uniform in length and number ofreferences However, in a few instances, two or more entries were combined into asingle longer entry Perhaps inevitably in a project with so many contributors, a smallnumber of entries were dropped because of personal issues, such as illness, thatinterfered with timely preparation of an entry Happily, contributors showed greatenthusiasm for this project, and their entries reﬂect an assembled expertise that ishigh tribute to the science and clinical practice in communication disorders

Raymond D Kent

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MITECD began as a promising idea in a conversation with Amy Brand, a previouseditor with MIT Press The idea was further developed, reﬁned, elaborated, and re-ﬁned again in many ensuing e-mail communications, and I thank Amy for her con-stant support and assistance through the early phases of the project When she leftMIT Press, Tom Stone, Senior Editor of Cognitive Sciences, Linguistics, and Brad-ford Books, stepped in to provide timely advice and attention I also thank MaryAvery, Acquisitions Assistant, for her help in keeping this project on track I amindebted to all of them

Speech, voice, language, and hearing are vast domains individually, and severalassociated editors helped to select topics for inclusion in MITECD and to identifycontributors with the necessary expertise The associate editors and their ﬁelds of re-sponsibility are as follows:

Fred H Bess, Ph.D., Hearing Disorders in Children

Joseph R Du¤y, Ph.D., Speech Disorders in Adults

Steven D Gray, M.D (deceased), Voice Disorders in Children

Robert E Hillman, Ph.D., Voice Disorders in Adults

Sandra Gordon-Salant, Ph.D., Hearing Disorders in Adults

Mabel L Rice, Ph.D., Language Disorders in Children

Lawrence D Shriberg, Ph.D., Speech Disorders in Children

David A Swinney, Ph.D., and Lewis P Shapiro, Ph.D., Language Disorders inAdults

The advice and cooperation of these individuals is gratefully acknowledged Sadly,

Dr Steven D Gray died within the past year He was an extraordinary man, andalthough I knew him only brieﬂy, I was deeply impressed by his passion for knowl-edge and life He will be remembered as an excellent physician, creative scientist, andvalued friend and colleague to many

Dr Houri Vorperian greatly facilitated this project through her inspired planning

of a computer-based system for contributor communications and record ment Sara Stuntebeck and Sara Brost worked skillfully and accurately on a variety

manage-of tasks that went into di¤erent phases manage-of MITECD They o¤ered vital help withcommunications, ﬁle management, proofreading, and the various and sundry tasksthat stood between the initial conception of MITECD and the submission of a fullmanuscript

P M Gordon and Associates took on the formidable task of assembling 200entries into a volume that looks and reads like an encyclopedia I thank DeniseBracken for exacting attention to the editing craft, creative solutions to unexpectedproblems, and forbearance through it all

MITECD came to reality through the e¤orts of a large number of contributors—too many for me to acknowledge personally here However, I draw the reader’s at-tention to the list of contributors included in this volume I feel a sense of communitywith all of them, because they believed in the project and worked toward its com-pletion by preparing entries of high quality I salute them not only for their con-tributions to MITECD but also for their many career contributions that deﬁne them

as experts in the ﬁeld I am honored by their participation and their patient ation with the editorial process

cooper-Raymond D Kent

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Part I: Voice

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Acoustic Assessment of Voice

Acoustic assessment of voice in clinical applications is

dominated by measures of fundamental frequency ( f0),

cycle-to-cycle perturbations of period ( jitter) and

inten-sity (shimmer), and other measures of irregularity, such

as noise-to-harmonics ratio (NHR) These measures are

widely used, in part because of the availability of

elec-tronic and microcomputer-based instruments (e.g., Kay

Elemetrics Computerized Speech Laboratory [CSL] or

Multispeech, Real-Time Pitch, Multi-Dimensional Voice

Program [MDVP], and other software/hardware

sys-tems), and in part because of long-term precedent for

perturbation (Lieberman, 1961) and spectral noise

measurements (Yanagihara, 1967) Absolute measures

of vocal intensity are equally basic but require

calibra-tions and associated instrumentation (Winholtz and

Titze, 1997)

Independently, these basic acoustic descriptors—f0,

intensity, jitter, shimmer, and NHR—can provide

some very basic characterizations of vocal health

The ﬁrst two, f0 and intensity, have very clear

percep-tual correlates—pitch and loudness, respectively—and

should be assessed for both stability and variability and

compared to age and sex norms (Kent, 1994; Baken

and Orliko¤, 2000) Ideally, these tasks are recorded

over headset microphones with direct digital acquisition

at very high sampling rates (at least 48 kHz) The

mate-rials to be assessed should be obtained following

stan-dardized elicitation protocols that include sustained

vowel phonations at habitual levels, levels spanning a

client’s vocal range in both f0 and intensity, running

speech, and speech tasks designed to elicit variation

(Titze, 1995; Awan, 2001) Note, however, that not all

measures will be appropriate for all tasks; perturbation

statistics, for example, are usually valid only when

extracted from sustained vowel phonations

These basic descriptors are not in any way

com-prehensive of the range of available measures or the

available signal properties and dimensions Table 1

cate-gorizes measures (Buder, 2000) based on primary basic

signal representations from which measures are derived

Although these categories are intended to be exhaustive

and mutually exclusive, some more modern algorithms

process components through several types (For more

detail on the measurement types, see Buder, 2000, and

Baken and Orliko¤, 2000.) Modern algorithmic

ap-proaches should be selected for (1) interpretability with

respect to aerodynamic and physiological models of

phonation and (2) the incorporation of multivariate

measures to characterize vocal function

Interdependence of Basic Measures The

interdepen-dence between f0 and intensity is mapped in a voice

range proﬁle, or phonetogram, which is an especially

valuable assessment for the professional voice user

(Coleman, 1993) Furthermore, the dependence of

per-turbations and signal-to-noise ratios on both f0 and

in-tensity is well known (Klingholz, 1990; Pabon, 1991)

This dependence is not often assessed rigorously, haps because of the time-consuming and strenuous na-ture of a full voice proﬁle However, an abbreviated orfocused proﬁling in which samples related to habitual f0

per-by a set number of semitones, or related to habitualintensity by a set number of decibels, could be stan-dardized to control for this dependence e‰ciently Fi-nally, it should be understood that perturbations andNHR-type measures will usually covary for many rea-sons, the simplest ones being methodological (Hillen-brand, 1987): an increase in any one of the underlyingphenomena detected by a single measure will also a¤ectthe other measures

Periodicity as a Reference The chief problem withnearly all acoustic assessments of voice is the determi-nation of f0 Most voice quality algorithms are based onthe prior identification of the periodic component in thesignal (based on glottal pulses in the time domain orharmonic structure in the frequency domain) Becausephonation is ideally a nearly periodic process, it islogical to conceive of voice measures in terms of the de-gree to which a given sample deviates from pure period-icity There are many conceptual problems with thissimplification, however At the physiological level, glot-tal morphology is multidimensional—superior-inferiorasymmetry is a basic feature of the two-mass model(Ishizaka and Flanagan, 1972), and some anterior-posterior asymmetry is also inevitable—rendering it un-likely that a glottal pulse will be marked by a discrete oreven a single instant of glottal closure At the level of thesignal, the deviations from periodicity may be eitherrandom or correlated, and in many cases they are so ex-treme as to preclude identification of a regular period.Finally, at the perceptual level, many factors related todeviations from a pure f0 can contribute to pitch per-ception (Zwicker and Fastl, 1990)

At any or all of these levels, it becomes questionable

to characterize deviations with pure periodicity as a erence In acoustic assessment, the primary level of con-cern is the signal The National Center for Voice and

ref-Table 1 Outline of Traditional Acoustic Algorithm Types

f0statisticsShort-term perturbationsLong-term perturbationsAmplitude statisticsShort-term perturbationsLong-term perturbations

f0/amplitude covariationsWaveform perturbationsSpectral measuresSpectrographic measuresFourier and LPC spectraLong-term average spectraCepstra

Inverse ﬁlter measuresRadiated signalFlow-mask signalsDynamic measures

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Speech issued a summary statement (Titze, 1995)

rec-ommending a typology for categorizing deviations from

periodicity in voices (see also Baken and Orliko¤, 2000,

for further subtypes) This typology capitalizes on the

categorical nature of dynamic states in nonlinear

sys-tems; all the major categories, including stable points,

limit cycles, period-doubling/tripling/ , and chaos can

be observed in voice signals (Herzel et al., 1994; Satalo¤

and Hawkshaw, 2001) As in most highly nonlinear

dynamic systems, deviations from periodicity can be

categorized on the basis of bifurcations, or sudden

qual-itative changes in vibratory pattern from one of these

states to another

Figure 1 displays a common form for one such

bifur-cation and illustrates the importance of accounting for

its presence in the application of perturbation measures

In this sustained vowel phonation by a middle-aged

woman with spasmodic dysphonia, a transition to

sub-harmonics is clearly visible in segment b (similar

pat-terns occur in individuals without dysphonias) Two f

extractions are presented for this segment, one at thetargeted level of approximately 250 Hz and anotherwhich the tracker ﬁnds one octave below this; inspec-tion of the waveform and a perceived biphonia bothjustify this 125-Hz analysis as a new fundamental fre-quency, although it can also be understood in thiscontext as a subharmonic to the original fundamen-tal There is therefore some ambiguity as to whichfundamental is valid during this episode, and an au-tomatic analysis could plausibly identify either frequency.(Here the waveform-matching algorithm implemented inCSpeechSP [Milenkovic, 1997] does identify either fre-quency, depending on where in the waveform the algo-rithm is applied; initiating the algorithm within thesubharmonic segment predisposes it to identify the lowerfundamental.)

The acoustic measures of the segments displayed inFigure 1 reveal the nontrivial di¤erences that result,depending on the basic glottal pulse form under consid-eration When the pulses of segment a are considered,

Figure 1.Approximately 900 ms of a sustained vowel

phona-tion waveform (top panel) with two fundamental frequency

analyses (bottom panel) Average f0, %jitter, %shimmer, and

SNR results for selected segments were from the ‘‘newjit’’ tine of TF32 program (Milenkovic, 2001)

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rou-the perturbations around rou-the base period associated with

the high f0 are low and normative; in segment b,

per-turbations around the longer periods of the lower f0 are

still low ( jitter is improved, while shimmer and the

signal-to-noise ratio show some degradation) However,

when all segments are considered together to include the

perturbations around the high f0 tracked through

seg-ment b and into c, the perturbation statistics are all

increased by an order of magnitude Many important

methodological and theoretical questions should be

raised by such common scenarios in which we must

consider not just voice typing, but the

segment-by-segment validity of applying perturbation measures with

a particular f0 as reference If, as is often assumed, jitter

and shimmer are ascribed to ‘‘random’’ variations, then

the correlated modulations of a strong subharmonic

ep-isode should be excluded Alternatively, the

perturba-tions might be analyzed with respect to the subharmonic

f0 In any case, assessment by means of perturbation

statistics with no consideration of their underlying

sources is unwise

Perceptual, Aerodynamic, and Physiological Correlates

of Acoustic Measures Regarding perceptual voice

rat-ings, Gerratt and Kreiman (2000) have critiqued tional assessments on several important methodologicaland theoretical points However, these points may notapply to acoustic analysis if (1) acoustic analysis is vali-dated on its own success and not exclusively in relation

tradi-to the problematic perceptual classiﬁcations, and (2)acoustic analysis is thoroughly grounded for interpreta-tion in some clear aerodynamic or physiological model

of phonation Gerratt and Kreiman also argue thatclinical classification may not be derived along a contin-uum that is defined with reference to normal qualities,but again, this argument may need to be reversed for theacoustic domain It is only by reference to a specificmodel that any assessment on acoustic grounds can beinterpreted (though this does not preclude development

of an independent model for a pathological phonatorymechanism) In clinical settings, acoustic voice assess-ment often serves to corroborate perceptual assessment.However, as guided by auditory experience and in con-junction with the ear and other instrumental assess-ments, careful acoustic analysis can be oriented to theidentiﬁcation of physiological status

In attempting to draw safe and reasonably directinferences from acoustic signal, aerodynamic models

Figure 2. Spectral features associated with models of phonation,

including the Liljencrants-Fant (LF) model of glottal ﬂow and

aperiodicity source models developed by Stevens The LF

model of glottal ﬂow is shown at top left At bottom left is the

LF model of glottal ﬂow derivative, showing the rate of change

in ﬂow At right is a spectrum schematic showing four e¤ects

These e¤ects include three derived parameters of the LF model:

(a) excitation strength (the maximum negative amplitude of the

ﬂow derivative, which is positively correlated with overall

har-monic energy), (b) dynamic leakage or non-zero return phase

following the point of maximum excitation (which is negatively

correlated with high-frequency harmonic energy), and (c) pulseskewing (which is negatively correlated with low-frequencyharmonic energy; this low-frequency region is also positivelycorrelated with open quotient and peak volume velocity mea-sures of the glottal ﬂow waveform) The e¤ect of turbulencedue to high airﬂow through the glottis is schematized by (d),indicating the associated appearance of high-frequency aperi-odic energy in the spectrum See voice acoustics for othergraphical and quantitative associations between glottal statusand spectral characteristics

Acoustic Assessment of Voice 5

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of glottal behavior present important links to the

physiological domain Attempts to recover the glottal

ﬂow waveform, either from a face mask-transduced

ﬂow recording (Rothenberg, 1973) or a

microphone-transduced acoustic recording (Davis, 1975), have

proved to be labor-intensive and prone to error (Nı´

Chasaide and Gobl, 1997) Rather than attempting to

eliminate the e¤ects of the vocal tract, it may be more

fruitful to understand its in situ relationship with

pho-nation, and infer, via the types of features displayed in

Figure 2, the status of the glottis as a sound source

In-terpretation of spectral features, such as the amplitudes

of the ﬁrst harmonics and at the formant frequencies,

may be an e¤ective alternative when guided by

knowl-edge of glottal aerodynamics and acoustics (Hanson,

1997; Nı´ Chasaide and Gobl, 1997; Hanson and

Chuang, 1999) Deep familiarity with acoustic

mecha-nisms is essential for such interpretations (Titze, 1994;

Stevens, 1998), as is a model with clear and meaningful

parameters, such as the Liljencrants-Fant (LF) model

(Fant, Liljencrants, and Lin, 1985) The parameters of

the LF model have proved to be meaningful in acoustic

studies (Gau‰n & Sundberg, 1989) and useful in reﬁned

e¤orts at inverse ﬁltering (Fro¨hlich, Michaelis, and

Strube, 2001) Figure 2 summarizes selected parameters

of the LF source model following Nı´ Chasaide and Gobl

(1997) and the glottal turbulence source following

Stevens (1998); see also voice acoustics for other

ap-proaches relating glottal status to spectral measures

Other spectral-based measures implement similar

model-based strategies by selecting spectral component

ratios (e.g., the VTI and SPI parameters of MDVP)

Sophisticated spectral noise characterizations control for

perturbations and modulations (Murphy, 1999; Qi,

Hillman, and Milstein, 1999), or employ curve-ﬁtting

and statistical models to produce more robust measures

(Alku, Strik, and Vilkman, 1997; Michaelis, Fro¨hlich,

and Strube, 1998; Schoentgen, Bensaid, and Bucella,

2000) A particularly valuable modern technique for

detecting turbulence at the glottis, the

glottal-to-noise-excitation ratio (Michaelis, Gramss, and Strube, 1997),

has been especially successful in combination with other

measures (Fro¨hlich et al., 2000) The use of acoustic

techniques for voice will only improve with the inclusion

of more knowledge-based measures in multivariate

rep-resentations (Wolfe, Cornell, and Palmer, 1991; Callen

et al., 2000; Wuyts et al., 2000)

—Eugene H Buder

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Aerodynamic Assessment of Vocal

Function

A number of methods have been used to quantitatively

assess the air volumes, airﬂows, and air pressures

in-volved in voice production The methods have been

mostly used in research to investigate mechanisms that

underlie normal and disordered voice and speech

pro-duction The clinical use of aerodynamic measures to

assess patients with voice disorders has been increasing

(Colton and Casper, 1996; Hillman, Montgomery, and

Zeitels, 1997; Hillman and Kobler, 2000)

Measurement of Air Volumes Respiratory research in

human communication has focused primarily on the

measurement of the air volumes that are typically

expended during selected speech and singing tasks, and

on specifying the ranges of lung inﬂation levels across

which such tasks are normally performed (cf Hixon,

Goldman, and Mead, 1973; Watson and Hixon, 1985;Hoit and Hixon, 1987; Hoit et al., 1990) Air volumesare measured in standard metric units (liters, cubic cen-timeters, milliliters) and lung inﬂation levels are usuallyspeciﬁed in terms of a percentage of the vital capacity ortotal lung volume

Both direct and indirect methods have been used tomeasure air volumes expended during phonation Directmeasurement of orally displaced air volumes duringphonatory tasks can be accomplished, to a limited ex-tent, by means of a mouthpiece or face mask connected

to a measurement device such as a spirometer (Beckett,1971) or pneumotachograph (Isshiki, 1964) The use of amouthpiece essentially limits speech production to sus-tained vowels, which are su‰cient for assessing selectedvolumetric-based phonatory parameters There are alsoconcerns that face masks interfere with normal jawmovements and that the oral acoustic signal is degraded,

so that auditory feedback is reduced or distorted andsimultaneous acoustic analysis is limited These limi-tations, which are inherent to the use of devices placed

in or around the mouth to directly collect oral airﬂow,plus additional measurement-related restrictions (Hill-man and Kobler, 2000) have helped motivate the de-velopment and application of indirect measurementapproaches

Most speech breathing research has been carried outusing indirect approaches for estimating lung volumes

by means of monitoring changes in body dimensions.The basic assumption underlying the indirect approaches

is that changes in lung volume are reﬂected in tional changes in body torso size One relatively cum-bersome but time-honored approach has been to placesubjects in a sealed chamber called a body plethysmo-graph to allow estimation of the air volume displaced bythe body during respiration (Draper, Ladefoged, andWhitteridge, 1959) More often used for speech breath-ing research are transducers (magnetometers: Hixon,Goldman, and Mead, 1973; inductance plethysmo-graphs: Sperry, Hillman, and Perkell, 1994) that unob-trusively monitor changes in the dimensions of the ribcage and abdomen (referred to collectively as the chestwall) that account for the majority of respiratory-relatedchanges in torso dimension (Mead et al., 1967) Theseapproaches have been primarily employed to study re-spiratory function during continuous speech and singingtasks that include both voiced and voiceless sound pro-duction, as opposed to assessing air volume usage duringphonatory tasks that involve only laryngeal production

propor-of voice (e.g., sustained vowels) There are also ongoinge¤orts to develop more accurate methods for non-invasively monitoring chest wall activity to capture ﬁnerdetails of how the three-dimensional geometry of thebody is altered during respiration (see Cala et al., 1996)

Measurement of Airflow Airflow associated with nation is usually specified in terms of volume velocity(i.e., volume of air displaced per unit of time) Volumevelocity airflow rates for voice production are typicallyreported in metric units of volume displaced (liters orcubic centimeters) per second

pho-Aerodynamic Assessment of Vocal Function 7

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Estimates of average airﬂow rates can be obtained by

simply dividing air volume estimates by the duration of

the phonatory task Average glottal airﬂow rates have

usually been estimated during vowel phonation by using

a mouthpiece or face mask to channel the oral air stream

through a pneumotachograph (Isshiki, 1964) There has

also been somewhat limited use of hot wire anemometer

devices (mounted in a mouthpiece) to estimate average

glottal airﬂow during sustained vowel phonation (Woo,

Colton, and Shangold, 1987) Estimates of average

glot-tal airﬂow rates can be obtained from the oral airﬂow

during vowel production because the vocal tract is

rela-tively nonconstricted, with no major sources of turbulent

airﬂow between the glottis and the lips

There have also been e¤orts to obtain estimates of the

actual airﬂow waveform that is generated as the glottis

rapidly opens and closes during ﬂow-induced vibration

of the vocal folds (the glottal volume velocity form) The glottal volume velocity waveform cannot bedirectly observed by measuring the oral airflow signalbecause the waveform is highly convoluted by the reso-nance activity (formants) of the vocal tract Thus, re-covery of the glottal volume velocity waveform requiresmethods that eliminate or correct for the influences ofthe vocal tract This has typically been accomplishedaerodynamically by processing the output of a fast-responding pneumotachograph (high-frequency re-sponse) using a technique called inverse filtering, inwhich the major resonances of the vocal tract are esti-mated and the oral airflow signal is processed (inversefiltered) to eliminate them (Rothenberg, 1977; Holm-berg, Hillman, and Perkell, 1988)

wave-Figure 1. Instrumentation and resulting signals forsimultaneous collection of oral airﬂow, intraoral airpressure, the acoustic signal, and chest wall (ribcage and abdomen) dimensions during production ofthe syllable string /pi-pi-pi/ Signals shown in thebottom panel are processed and measured to provideestimates of average glottal airﬂow rate, averagesubglottal air pressure, lung volume, and glottalwaveform parameters

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Measurement of Air Pressure Measurements of air

pressures below (subglottal) and above (supraglottal) the

vocal folds are of primary interest for characterizing the

pressure di¤erential that must be achieved to initiate and

maintain vocal fold vibration during normal

exhala-tory phonation In practice, air pressure measurements

related speciﬁcally to voice production are typically

acquired during vowel phonation when there are no

vocal tract constrictions of su‰cient magnitude to build

up positive supraglottal pressures Under these

condi-tions, it is usually assumed that supraglottal pressure is

essentially equal to atmospheric pressure and only

sub-glottal pressure measurements are obtained Air

pres-sures associated with voice and speech production are

usually speciﬁed in centimeters of water (cm H2O)

Both direct and indirect methods have been used to

measure subglottal air pressures during phonation

Di-rect measures of subglottal air pressure can be obtained

by inserting a hypodermic needle into the subglottal

air-way through a puncture in the anterior neck at the

cri-cothyroid space (Isshiki, 1964) The needle is connected

to a pressure transducer by tubing This method is very

accurate but also very invasive It is also possible to

in-sert a very thin catheter through the posterior

cartilagi-nous glottis (between the arytenoids) to sense subglottal

air pressure during phonation, or to use an array of

miniature transducers positioned directly above and

be-low the glottis (Cranen and Boves, 1985) These methods

cannot be tolerated by all subjects, and the heavy topical

anesthetization of the larynx that is required can a¤ect

normal function

Indirect estimates of tracheal (subglottal) air pressure

can be obtained via the placement of an elongated

balloon-like device into the esophagus (Liberman, 1968)

The deﬂated esophageal balloon is attached to a catheter

that is typically inserted transnasally and then swallowed

into the esophagus to be positioned at the midthoracic

level The catheter is connected to a pressure transducer

and the balloon is slightly inﬂated Accurate use of this

invasive method also requires simultaneous monitoring

of lung volume

Noninvasive, indirect estimates of subglottal air

sure can be obtained by measuring intraoral air

pres-sure during specially constrained utterances (Smitheran

and Hixon, 1981) This is usually done by sensing air

pressure just behind the lips with a translabially placed

catheter connected to a pressure transducer These

intraoral pressure measures are obtained as subjects

produce strings of bilabial /p/þ vowel syllables (e.g.,

/pi-pi-pi-pi-pi/) at constant pitch and loudness This

method works because the vocal folds are abducted

during /p/ production, thus allowing pressure to

equili-brate throughout the airway, making intraoral pressure

equal to subglottal pressure (Fig 1)

Additional Derived Measures There have been

numer-ous attempts to extend the utility of aerodynamic

mea-sures by using them in the derivation of additional

parameters aimed at better elucidating underlying

mechanisms of vocal function Such derived measures

usually take the form of ratios that relate aerodynamicparameters to each other, or that relate aerodynamicparameters to simultaneously obtained acoustic mea-sures Common examples include (1) airway (glottal)resistance (see Smitheran and Hixon, 1981), (2) vocale‰ciency (Schutte, 1980; Holmberg, Hillman, and Per-kell, 1988), and (3) measures that interrelate glottalvolume velocity waveform parameters (Holmberg, Hill-man, and Perkell, 1988)

Normative Data As is the case for most measures ofvocal function, there is not currently a set of normativedata for aerodynamic measures that is universallyaccepted and applied in research and clinical work.Methods for collecting such data have not been stan-dardized, and study samples have generally not been ofsu‰cient size or appropriately stratiﬁed in terms of ageand sex to ensure unbiased estimates of underlying aero-dynamic phonatory parameters in the normal popula-tion However, there are several sources in the literaturethat provide estimates of normative values for selectedaerodynamic measures (Kent, 1994; Baken, 1996; Col-ton and Casper, 1996)

See also voice production: physics and physiology

Cala, S J., Kenyon, C M., Ferrigno, G., Carnevali, P.,Aliverti, A., Pedotti, A., et al (1996) Chest wall and lungvolume estimation by optical reﬂectance motion analysis.Journal of Applied Physiology, 81, 2680–2689

Colton, R H., and Casper, J K (1996) Understanding voiceproblems: A physiological perspective for diagnosis andtreatment Baltimore: Williams and Wilkins

Cranen, B., and Boves, L (1985) Pressure measurements ing speech production using semiconductor miniature pres-sure transducers: Impact on models for speech production.Journal of the Acoustical Society of America, 77, 1543–1551

dur-Draper, M., Ladefoged, P., and Whitteridge, P (1959) ratory muscles in speech Journal of Speech and HearingResearch, 2, 16–27

Respi-Hillman, R E., and Kobler, J B (2000) Aerodynamic sures of voice production In R Kent and M Ball (Eds.),The handbook of voice quality measurement, San Diego, CA:Singular Publishing Group

mea-Hillman, R E., Montgomery, W M., and Zeitels, S M.(1997) Current diagnostics and o‰ce practice: Use of ob-jective measures of vocal function in the multidisciplin-ary management of voice disorders Current Opinion inOtolaryngology–Head and Neck Surgery, 5, 172–175.Hixon, T J., Goldman, M D., and Mead, J (1973) Kine-matics of the chest wall during speech production: Volumedisplacements of the rib cage, abdomen, and lung Journal

of Speech and Hearing Research, 16, 78–115

Hoit, J D., and Hixon, T J (1987) Age and speech breathing.Journal of Speech and Hearing Research, 30, 351–366

Aerodynamic Assessment of Vocal Function 9

Trang 24

Hoit, J D., Hixon, T J., Watson, P J., and Morgan, W J.

(1990) Speech breathing in children and adolescents

Jour-nal of Speech and Hearing Research, 33, 51–69

Holmberg, E B., Hillman, R E., and Perkell, J S (1988)

Glottal airﬂow and transglottal air pressure measurements

for male and female speakers in soft, normal, and loud

voice [published erratum appears in Journal of the

Acousti-cal Society of America, 1989, 85(4), 1787] Journal of the

Acoustical Society of America, 84, 511–529

Isshiki, N (1964) Regulatory mechanisms of vocal intensity

variation Journal of Speech and Hearing Research, 7,

17–29

Kent, R D (1994) Reference manual for communicative

sciences and disorders San Diego, CA: Singular Publishing

Group

Lieberman, P (1968) Direct comparison of subglottal and

esophageal pressure during speech Journal of the Acoustical

Society of America, 43, 1157–1164

Mead, J., Peterson, N., Grimgy, N., and Mead, J (1967)

Pul-monary ventilation measured from body surface

move-ments Science, 156, 1383–1384

Rothenberg, M (1977) Measurement of airﬂow in speech

Journal of Speech and Hearing Research, 20, 155–176

Schutte, H (1980) The e‰ciency of voice production

Gronin-gen, The Netherlands: Kemper

Smitheran, J R., and Hixon, T J (1981) A clinical method

for estimating laryngeal airway resistance during vowel

production Journal of Speech and Hearing Disorders, 46,

138–146

Sperry, E., Hillman, R E., and Perkell, J S (1994) The use of

an inductance plethysmograph to assess respiratory

func-tion in a patient with nodules Journal of Medical

Speech-Language Pathology, 2, 137–145

Watson, P J., and Hixon, T J (1985) Respiratory kinematics

in classical (opera) singers Journal of Speech and Hearing

Research, 28, 104–122

Woo, P., Colton, R H., and Shangold, L (1987) Phonatory

airﬂow analysis in patients with laryngeal disease Annals of

Otology, Rhinology, and Laryngology, 96, 549–555

Alaryngeal Voice and Speech

Rehabilitation

Loss of the larynx due to disease or injury will result in

numerous and signiﬁcant changes that cross anatomical,

physiological, psychological, social, psychosocial, and

communication domains Surgical removal of the

lar-ynx, or total laryngectomy, involves resectioning the

entire framework of the larynx Although total

laryn-gectomy may occur in some instances due to traumatic

injury, the majority of cases worldwide are the result of

cancer Approximately 75% of all laryngeal tumors arise

from squamous epithelial tissue of the true vocal fold

(Bailey, 1985) In some instances, and because of the

location of many of these lesions, less aggressive

ap-proaches to medical intervention may be pursued This

may include radiation therapy or partial surgical

resec-tion, which seeks to conserve portions of the larynx, or

the use of combined chemoradiation protocols (Hillman

et al., 1998; Orliko¤ et al., 1999) However, when

ma-lignant lesions are su‰ciently large or when the location

of the tumor threatens the lymphatic compartment of

the larynx, total laryngectomy is often indicated for sons of oncological safety (Doyle, 1994)

rea-E¤ects of Total Laryngectomy

The two most prominent e¤ects of total laryngectomy as

a surgical procedure are change of the normal airwayand loss of the normal voicing mechanism for verbalcommunication Once the larynx is surgically removedfrom the top of the trachea, the trachea is brought for-ward to the anterior midline neck and sutured into placenear the sternal notch Thus, total laryngectomy neces-sitates that the airway be permanently separated fromthe upper aerodynamic (oral and pharyngeal) pathway.When the laryngectomy is completed, the tracheal air-way will remain separate from the oral cavity, pharynx,and esophagus Under these circumstances, not only isthe primary structure for voice generation lost, but theintimate relationship between the pulmonary system andthat of the structures of the upper airway, and con-sequently the vocal tract, is disrupted Therefore, ifverbal communication is to be acquired and used post-laryngectomy, an alternative method of creating analaryngeal voice source must be achieved

Methods of Postlaryngectomy Communication

Following laryngectomy, the most signiﬁcant cative component to be addressed via voice and speechrehabilitation is the lost voice source Once the larynx isremoved, some alternative method of providing a new,

communi-‘‘alaryngeal’’ sound source is required There are twogeneral categories in which an alternative, alaryngealvoice source may be achieved These categories are bestdescribed as intrinsic and extrinsic methods The dis-tinction between these two methods is contingent on themanner in which the alaryngeal voice source is achieved.Intrinsic alaryngeal methods imply that the alaryngealvoice source is found within the system; that is, alterna-tive physical-anatomical structures are used to generatesound In contrast, extrinsic methods of alaryngealspeech rely on the use of an external sound source, typi-cally an electronic source, or what is termed the artiﬁciallarynx, or the electrolarynx The fundamental di¤erencesbetween intrinsic and extrinsic methods of alaryngealspeech are discussed below

Intrinsic Methods of Alaryngeal SpeechThe two most prominent methods of intrinsic alaryngealspeech are esophageal speech (Diedrich, 1966; Doyle,1994) and tracheoesophageal (TE) speech (Singer andBlom, 1980) While these two intrinsic methods ofalaryngeal speech are dissimilar in some respects, bothrely on generation of an alaryngeal voice source by cre-ating oscillation of tissues in the area of the lower phar-ynx and upper esophagus This vibratory structure issomewhat variable in regard to width, height, and loca-tion (Diedrich and Youngstrom, 1966; Damste, 1986);hence, the preferred term for this alaryngeal voicingsource is the pharyngoesophageal (PE) segment One

Trang 25

muscle that comprises the PE segment is the

cricophar-yngeal muscle Beyond the commonality in the use of the

PE segment as a vicarious voicing source for both

esophageal and TE methods of alaryngeal speech, the

manner in which these methods are achieved does di¤er

Esophageal Speech For esophageal speech, the

speaker must move air from the oral cavity across the

tonically closed PE segment in order to insu¿ate

the esophageal reservoir (located inferior to the PE

seg-ment) Two methods of insu¿ation may be utilized

These methods might be best described as being either

direct or indirect approaches to insu¿ation Direct

methods require the individual speaker to actively

ma-nipulate air in the oral cavity to e¤ect a change in

pres-sure When pressure build-up is achieved in the oral

cavity via compression maneuvers, and when the

pres-sure becomes of su‰cient magnitude to overcome the

muscular resistance of the PE segment, air will move

across the segment (inferiorly) into the esophagus This

may be accomplished with nonspeech tasks (tongue

maneuvers) or as a result of producing speciﬁc sounds

(e.g., stop consonants)

In contrast, for the indirect (inhalation) method of air

insu¿ation, the speaker indirectly creates a negative

pressure in the esophageal reservoir via rapid inhalation

through the tracheostoma This results in a negative

pressure in the esophagus relative to the normal

atmo-spheric pressure within the oral cavity/vocal tract

(Die-drich and Youngstrom, 1966; Die(Die-drich, 1968; Doyle,

1994) Air then moves passively across the PE segment

in order to equalize pressures between the pharynx and

esophagus Once insu¿ation occurs, this air can be used

to generate PE segment vibration in the same manner

following other methods of air insu¿ation While a

dis-tinction between direct and indirect methods permits

increased understanding of the physical requirements

for esophageal voice production, many esophageal

speakers who exhibit high levels of proﬁciency will often

utilize both methods for insu¿ation Regardless of

which method of air insu¿ation is used, this air can then

be forced back up across the PE segment, and as a result,

the tissue of this sphincter will oscillate This esophageal

sound source can then be manipulated in the upper

regions of the vocal tract into the sounds of speech

The acquisition of esophageal speech is a complex

process of skill building that must be achieved under the

direction of an experienced instructor Clinical emphasis

typically involves tasks that address four skills believed

to be fundamental to functional esophageal speech

(Berlin, 1963): (1) the ability to phonate reliably on

de-mand, (2) the ability to maintain a short latency between

air insu¿ation and esophageal phonation, (3) the ability

to maintain adequate duration of voicing, and (4) the

ability to sustain voicing while articulating These

foun-dation skills have been shown to reﬂect those progressive

abilities that have historically deﬁned speech skills of

‘‘superior’’ esophageal speakers (Wepman et al., 1953;

Snidecor, 1968) However, the successful acquisition of

esophageal speech may be limited, for many reasons

Regardless of which method of insu¿ation is used,esophageal speakers will exhibit limitations in the phy-sical dimensions of speech Speciﬁcally, fundamentalfrequency is reduced by about one octave (Curry andSnidecor, 1961), intensity is reduced by about 10 dB SPLfrom that of the normal speaker (Weinberg, Horii, andSmith, 1980), and the durational characteristics ofspeech are also reduced Speech intelligibility is alsodecreased due to limits in the aerodynamic and voicingcharacteristics of esophageal speech As it is not anabductory-adductory system, voiced-for-voiceless per-ceptual errors (e.g., perceptual identiﬁcation of b for p)are common This is a direct consequence of the esoph-ageal speaker’s inability to insu¿ate large or continuousvolumes of air into the reservoir Esophageal speakersmust frequently reinsu¿ate the esophageal reservoir tomaintain voicing Because of this, it is not uncommon tosee esophageal speakers exhibit pauses at unusual points

in an utterance, which ultimately alters the normalrhythm of speech Similarly, the prosodic contour ofesophageal speech and associated features is often per-ceived to be abnormal In contrast to esophageal speech,the TE method capitalizes on the individual’s access topulmonary air for esophageal insu¿ation, which o¤ersseveral distinct advantages relative to esophageal speech

Tracheoesophageal Speech TE speech uses the samevoicing source as traditional esophageal speech, the PEsegment However, in TE speech the speaker is able toaccess and use pulmonary air as a driving source This isachieved by the surgical creation of a controlled midlinepuncture in the trachea, followed by insertion of a one-way TE puncture voice prosthesis (Singer and Blom,1980), either at the time of laryngectomy or as a secondprocedure at some point following laryngectomy Thus,

TE speech is best described as a surgical-prostheticmethod of voice restoration Though widely used, TEvoice restoration is not problem-free Limitations inapplication must be considered, and complications mayoccur

The design of the TE puncture voice prosthesis is suchthat when the tracheostoma is occluded, either by hand

or via use of a complementary tracheostoma breathingvalve, air is directed from the trachea through the pros-thesis and into the esophageal reservoir This accesspermits a variety of frequency, intensity, and durationalvariables to be altered in a fashion di¤erent from that ofthe traditional esophageal speaker (Robbins et al., 1984;Pauloski, 1998) Because the TE speaker has direct ac-cess to a pulmonary air source, his or her ability tomodify the physical (frequency, intensity, and dura-tional) characteristics of the signal in response tochanges in the aerodynamic driving source, along withassociated changes in prosodic elements of the speechsignal (i.e., stress, intonation, juncture), is enhancedconsiderably Such changes have a positive impact onauditory-perceptual judgments of this method of alaryn-geal speech

While the frequency of TE speech is still reduced fromthat of normal speech, the intensity is greater, and the

Alaryngeal Voice and Speech Rehabilitation 11

Trang 26

durational capabilities meet or exceed those of normal

speakers (Robbins et al., 1984) Finally, research into

the inﬂuence of increased aerodynamic support in TE

speakers relative to traditional esophageal speech on

speech intelligibility has suggested that positive e¤ects

may be observed (Doyle, Danhauer, and Reed, 1988)

despite continued voiced-for-voiceless perceptual errors

Clearly, the rapidity of speech reacquisition in addition

to the relative increases in speech intelligibility and the

changes in the overall physical character of TE speech

o¤ers considerable advantages from the perspective of

communication rehabilitation

Artiﬁcial Laryngeal Speech Extrinsic methods of

alaryngeal voice production are common Although

some pneumatic devices have been introduced, they are

not widely used today The most frequently used

extrin-sic method of producing alaryngeal speech uses an

elec-tronic artiﬁcial larynx, or electrolarynx These devices

provide an external energy (voice) source that is

intro-duced either directly into the oral cavity (intraoral) or by

placing a device directly on the tissues of the neck

(transcervical) Whether the electrolaryngeal tone is

introduced into the oral cavity directly or through

transmission via tissues of the neck, the speaker is able to

modulate the electrolaryngeal source into speech

The electrolayrnx is generally easy to use Speech

can be acquired relatively quickly, and the device o¤ers

a reasonable method of functional communication to

those who have undergone total laryngectomy (Doyle,

1994) Its major limitations have traditionally related to

negative judgments of electrolaryngeal speech relative to

the mechanical nature of many devices Current research

is seeking to modify the nature of the electronic sound

source produced The intelligibility of electrolaryngeal

speech is relatively good, given the external nature of the

alaryngeal voice source and the electronic character of

sound production A reduction in speech intelligibility is

primarily observed for voiceless consonants (i.e.,

voiced-for-voiceless errors) due to the fact that the electrolarynx

is a continuous sound source (Weiss and Basili, 1985)

Rehabilitative Considerations

All methods of alaryngeal speech, whether esophageal,

TE, or electrolaryngeal, have distinct advantages and

disadvantages Advantages for esophageal speech include

a nonmechanical and hands-free method of

communi-cation For TE speech, pitch is near normal, loudness

exceeds normal, and speech rate and prosody is near

normal; for artiﬁcial larynx speech, it may be acquired

quickly by most people and may be used in conditions of

background noise In contrast, disadvantages for

esoph-ageal speech include lowered pitch, loudness, and speech

rate For TE speech, it involves use and maintenance of

a prosthetic device with associated costs; for artiﬁcial

larynx speech, a mechanical quality is common and it

requires the use of one hand While ‘‘normal’’ speech

cannot be restored with these methods, no matter how

proﬁcient the speaker’s skills, all methods are viable

postlaryngectomy communication options, and at least

one method can be used with a functional tive outcome in most instances Professionals who workwith individuals who have undergone total laryngectomymust focus on identifying a method that meets eachspeaker’s particular needs Although clinical interven-tion must focus on making any given alaryngeal method

communica-as proﬁcient communica-as possible, the individual speaker’s needs,

as well as the relative strengths and weaknesses of eachmethod, must be considered In this way, use of a givenmethod may be enhanced so that the individual mayachieve the best level of social reentry following lar-yngectomy Further, nothing prevents an individualfrom using multiple methods of alaryngeal speech, al-though one or another may be preferred in a givencommunication context or environment But an im-portant caveat is necessary: Just because a method ofalaryngeal speech has been acquired and it has beendeemed ‘‘proﬁcient’’ at the clinical level (e.g., results ingood speech intelligibility) and is ‘‘functional’’ for basiccommunication purposes, this does not imply that ‘‘re-habilitation’’ has been successfully achieved

The reacquisition of verbal communication is withoutquestion a critical component of recovery and rehabili-tation postlaryngectomy; however, it is only one dimen-sion of the complex picture of a successful return to asnormal a life as possible All individuals who have un-dergone a laryngectomy will confront myriad restrictions

in multiple domains, including anatomical, logical, psychological, communicative, and social As aresult, postlaryngectomy rehabilitation e¤orts that ad-dress these areas may increase the likelihood of a suc-cessful postlaryngectomy outcome

physio-See also laryngectomy

—Philip C Doyle and Tanya L Eadie

References

Bailey, B J (1985) Glottic carcinoma In B J Bailey and

H F Biller (Eds.), Surgery of the larynx (pp 257–278).Philadelphia: Saunders

Berlin, C I (1963) Clinical measurement of esophagealspeech: I Methodology and curves of skill acquisition.Journal of Speech and Hearing Disorders, 28, 42–51.Curry, E T., and Snidecor, J C (1961) Physical measurementand pitch perception in esophageal speech Laryngoscope,

71, 415–424

Damste, P H (1986) Some obstacles to learning esophagealspeech In R L Keith and F L Darley (Eds.), Laryn-gectomee rehabilitation (2nd ed., pp 85–92) San Diego:College-Hill Press

Diedrich, W M (1968) The mechanism of esophageal speech.Annals of the New York Academy of the Sciences, 155,303–317

Diedrich, W M., and Youngstrom, K A (1966) Alaryngealspeech Springﬁeld, IL: Charles C Thomas

Doyle, P C (1994) Foundations of voice and speech tation following laryngeal cancer San Diego, CA: SingularPublishing Group

rehabili-Doyle, P C., Danhauer, J L., and Reed, C G (1988) teners’ perceptions of consonants produced by esophagealand tracheoesophageal talkers Journal of Speech andHearing Disorders, 53, 400–407

Trang 27

Lis-Hillman, R E., Walsh, M J., Wolf, G T., Fisher, S G., and

Hong, W K (1998) Functional outcomes following

treat-ment for advanced laryngeal cancer Annals of Otology,

Rhinology and Laryngology, 107, 2–27

Orliko¤, R F., Kraus, D S., Budnick, A S., Pﬁster, D G.,

and Zelefsky, M J (1999) Vocal function following

suc-cessful chemoradiation treatment for advanced laryngeal

cancer: Preliminary results Phonoscope, 2, 67–77

Pauloski, B R (1998) Acoustic and aerodynamic

character-istics of tracheoesophageal voice In E D Blom, M I

Singer, and R C Hamaker (Eds.), Tracheoesophageal voice

restoration following total laryngectomy (pp 123–141) San

Diego, CA: Singular Publishing Group

Robbins, J., Fisher, H B., Blom, E D., and Singer, M I

(1984) A comparative acoustic study of normal,

esopha-geal, and tracheoesophageal speech production Journal of

Speech and Hearing Disorders, 49, 202–210

Singer, M I., and Blom, E D (1980) An endoscopic

tech-nique for restoration of voice after laryngectomy Annals of

Otology, Rhinology, and Laryngology, 89, 529–533

Snidecor, J C (1968) Speech rehabilitation of the

laryngec-tomized Springﬁeld, IL: Charles C Thomas

Weiss, M S., and Basili, A M (1985) Electrolaryngeal speech

produced by laryngectomized subjects: Perceptual

char-acteristics Journal of Speech and Hearing Research, 28,

294–300

Wepman, J M., MacGahan, J A., Rickard, J C., and

Shel-ton, N W (1953) The objective measurement of

progres-sive esophageal speech development Journal of Speech and

Hearing Disorders, 18, 247–251

Further Readings

Fink, B (1975) The human larynx New York: Raven Press

Hast, M H (1970) The developmental anatomy of the larynx

Otolaryngology Clinics of North America, 3, 413–438

Hirano, M (1981) Structure of the vocal fold in normal and

disease states anatomical and physical studies In C L

Ludlow and M O Hart (Eds.), Proceedings of the

Confer-ence on the Assessment of Vocal Pathology (ASHA Reports

11) Rockville, MD: American Speech-Language-Hearing

Assoc

Hirano, M., and Sato, K (1993) Histological color atlas of the

human larynx San Diego, CA: Singular Publishing Group

Kahane, J C (1998) Functional histology of the larynx

and vocal folds In C W Cummings, J M Frederickson,

L A Harker, C J Krause, and D E Schuller (Eds.),

Otolaryngology Head and Neck Surgery (pp 1853–1868)

St Louis: Mosby

Konig, W F., and von Leden, H (1961) The peripheral

ner-vous system of the human larynx: I The mucous

mem-brane Archives of Otolaryngology, 74, 1–14

Negus, V (1928) The mechanism of the larynx St Louis:

Mosby

Orliko¤, R F., and Kahane, J C (1996) Structure and

func-tion of the larynx In N J Lass (Ed.), Principles of

experi-mental phonetics St Louis: Mosby

Rossi, G., and Cortesina, G (1965) Morphological study of

the laryngeal muscles in man: Insertions and courses of

muscle ﬁbers, motor end-plates and proprioceptors Acta

Otolaryngologica, 59, 575–592

Assessment of Functional Impact of

Voice Disorders

Introduction

Voice disorders occur in approximately 6% of all adults

and in as many as 12% of children Within the adult

group, speciﬁc professions report the presence of a voice

problem that interferes with their employment As many

as 50% of teachers and 33% of secretaries complain of

voice problems that restrict their ability to work or to

function in a normal social environment (Smith et al.,

1998) The restriction of work, or lifestyle, due to a voice

disorder has gone virtually undocumented until recently

While voice scientists and clinicians have focused most

of their energy, talent, and time on diagnosing and

measuring the severity of voice disorders with various

perceptual, acoustic, or physiological instruments, little

attention has been given to the e¤ects of a voice disorder

on the daily needs of the patient Over the past few

years, interest has increased in determining the

func-tional impact of the voice disorder due to the Internet in

using patient-based outcome measures to establish

e‰-cacy of treatments and the desire to match treatment

needs with patient’s needs This article reviews the

evo-lution of the assessment of functional impact of voice

disorders and selected applications of those assessments

Assessment of the physiological consequences of

voice disorders has evolved from a strong interest in the

relationship of communication ability to global of-life measurement Hassan and Weymuller (1993), List

quality-et al (1998), Picarillo (1994), and Murry quality-et al (1998)have all demonstrated that voice communication is anessential element in patients’ perception of their quality

of life following treatment for head and neck cancer.Patient-based assessment of voice handicap has beenlacking in the area of noncancerous voice disorders Thedevelopments and improvements of software for assess-ing acoustic objective measures of voice and relatingmeasures of abnormal voices to normal voices have gone

on for a number of years However, objective measuresprimarily assess specific treatments and do not encom-pass functional outcomes from the patient’s perspective.These measures do not necessarily discriminate the se-verity of handicap as it relates to specific professions.Objective test batteries are useful to quantify disease se-verity (Rosen, Lombard, and Murry, 2000), categorizeacoustic/physiological profiles of the disease (Hartl et al.,2001), and measure changes that occur as a result oftreatment (Dejonckere, 2000) A few objective and sub-jective measures are correlated with the diagnosis ofthe voice disorder (Wolfe, Fitch, and Martin, 1997), butuntil recently, none have been related to the patient’sperception of the severity of his or her problem Thislatter issue is important in all diseases and disorderswhen life is not threatened since it is ultimately thepatient’s perception of disease severity and his or hermotivation to seek treatment that dictates the degree oftreatment success

Functional impact relates to the degree of handicap

or disability Accordingly, there are three levels of adisorder: impairment, disability, and handicap (WorldHealth Organization, 1980) Handicap is the impact ofthe impairment of the disability on the social, environ-mental, or economic functioning of the individual.Treatment usually relates to the physical well-being of apatient, and it is this physical well-being that generallytakes priority when attempting to assess the severity ofthe handicap A more comprehensive approach mightseek to address the patient’s own impression of the se-verity of the disorder and how the disorder interfereswith the individual’s professional and personal lifestyle.Measurement of functional impact is somewhatdi¤erent from assessment of disease status in that itdoes not directly address treatment e‰cacy, but ratheraddresses the value of a particular treatment for a par-ticular individual This may be considered treatment ef-fectiveness E‰cacy, on the other hand, looks at whether

or not a treatment can produce an expected result based

on previous studies Functional impact relates to the gree of impact a disorder has on an individual patient,not necessarily to the severity of the disease

de-Voice Disorders and Outcomes Research

Assessment of functional impact on the voice is barelybeyond the infancy stage Interest in the issues relating tofunctional use of the voice stems from the development

of instruments to measure all aspects of vocal functionrelated to the patient, the disease, and the treatment

Trang 35

Moreover, there are certain parameters of voice

dis-orders that cannot be easily measured in the voice

labo-ratory, such as endurance, acceptance of a new voice,

and vocal e¤ectiveness

The measurement of voice handicap must take into

account issues such as ‘‘can the person teach in the

classroom all day?’’ or ‘‘can a shop foreman talk loud

enough to be heard over the noise of factory machines?’’

An outcome measure that takes into account the

patient’s ability to speak in the classroom or a factory

will undoubtedly provide a more accurate assessment

of voice handicap (although not necessarily an accurate

assessment of the disease, recovery from disease, or

quality of voice) than the acoustic measures obtained in

the voice laboratory Thus, patient-based measures of

voice handicap provide signiﬁcant information that

can-not be obtained from biological and physiologic

vari-ables traditionally used in voice assessment models

Voice handicap measures may measure an

individu-al’s perceived level of general health, an individuindividu-al’s

quality of life, her ability to continue with her current

employment versus opting for a change in employment,

her satisfaction with treatment regardless of the disease

state, or the cost of the treatment Outcome of treatment

for laryngeal cancer is typically measured using

Kaplan-Myer curves (Adelstein et al., 1990) While this tool

measures the disease-related status of the patient, it does

not presume to assess overall patient satisfaction with

treatment Rather, the degree to which swallowing status

improves and voice communication returns to normal

are measured by instruments that generally focus on

quality of life (McHorney et al., 1993)

Voice disorders are somewhat di¤erent than the

treatment of a life threatening disease such as laryngeal

cancer Treatment that involves surgery, pharmacology,

or voice therapy requires the patient’s full cooperation

throughout the course of treatment The quality and

ac-curacy of surgery or the level of voice therapy may not

necessarily reﬂect the long-term outcome if the patient

does not cooperate with the treatment procedure

As-sessment of voice handicap involves the patient’s ability

to use his or her voice under normal circumstances of

social and work-related speaking situations The voice

handicap will be reﬂected to the extent that the voice is

usable in those situations

Outcome Measures: General Health Versus

Speciﬁc Disease

There are two primary ways to assess the handicap of

a voice disorder One is to look at the patient’s overall

well-being The other is to compare his or her voice to

normal voice measures The ﬁrst usually encompasses

social factors as well as physical factors that are related

to the speciﬁc disorder One measure that has been used

to look at the e¤ect of disease on life is the Medical

Outcomes Study (MOS), a 36-item short-form general

health survey (McHorney et al., 1993) The 36-item

short form, otherwise known as SF-36, measures eight

areas of health that are commonly a¤ected or changed

by diseases and treatments: physical functioning, role

functioning, bodily pain, general health, vitality, socialfunctioning, mental health, and health transition TheSF-36 has been used for a wide range of disease-specifictopics once it was shown to be a valid measure ofthe degree of general health The SF-36 is a pencil-and-paper test that has been used in numerous studies forassessing outcomes of treatment In addition, becauseeach scale has been determined to be a reliable and validmeasure of health in and of itself, this assessment hasbeen used to validate other assessments of quality of lifeand handicap that are disease specific However, one ofthe di‰culties with using such a test for a specific disease

is that one or more of the subscales may not be tant or appropriate For example, when considering cer-tain voice disorders, the subscale of the SF-36 known asbodily pain may not be quite appropriate Thus, the SF-

impor-36 is not a direct assessment of voice handicap but rather

a general measure of well-being

The challenge to develop a speciﬁc scale related to aspeciﬁc organ function such as a scale for voice disorderspresents problems unlike the development of the SF-36

or other general quality-of-life scales

Assessing Voice Handicap

Currently there are no federal regulations deﬁning voicehandicap, unlike the handicap measures associated withhearing loss, which is regulated by the Department ofLabor The task of measuring the severity of a voicedisorder may be somewhat di‰cult because of the areasthat are a¤ected, namely emotional, physical, functional,economic, etc Moreover, as already indicated, whilemeasures such a perceptual judgments of voice charac-teristics, videostroboscopic visual perceptual ﬁndings,acoustic perceptual judgments, as well as physiologicalmeasures objectively obtained provide some input as

to the severity of the voice compared to normal, thesemeasures do not provide insight as to the degree ofhandicap and disability that a speciﬁc patient is experi-encing It should be noted, however, that there arehandicap/disability measures developed for other aspects

of communication, namely hearing loss and dizziness(Newman et al., 1990; Jacobson et al., 1994) Thesemeasures have been used to quantify functional outcomefollowing various interventions in auditory function

Development of the Voice Handicap Index

In 1997, Jacobson and her colleagues proposed a sure of voice handicap known as the Voice HandicapIndex (VHI) (Jacobson et al., 1998) This patient self-assessment tool consists of ten items in each of threedomains: emotional, physical, and functional aspects ofvoice disorders The functional subscale includes state-ments that describe the impact of a person’s voice onhis daily activities The emotional subscale indicates thepatient’s a¤ective responses to the voice disorder Theitems in the physical subscale are statements that relate

mea-to either the patient’s perception of laryngeal discomfort

or the voice output characteristics such as too low or toohigh a pitch From an original 85-item list, a 30-itemAssessment of Functional Impact of Voice Disorders 21

Trang 36

questionnaire using a ﬁve-point response scale from 0,

indicating he ‘‘never’’ felt this about his voice problem to

4, where he ‘‘always’’ felt this to be the case, was ﬁnally

obtained This 30-item questionnaire was then assessed

for test-retest stability in total as well as the three

sub-scales, and was validated against the SF-36 A shift in

the total score of 18 points or greater is required in order

to be certain that a change is due to intervention and not

to unexplained variability The Voice Handicap Index

was designed to assess all types of voice disorders, even

those encountered by tracheoesophageal speakers A

detailed analysis of patient data using this test has

recently been published (Benninger et al., 1998)

Since the VHI has been published, others have

pro-posed similar tests of handicap Hogikian (1999) and

Glicklich (1999) have both demonstrated their

assess-ment tools to have validity and reliability in assessing a

patient’s perception of the severity of a voice problem

One of the additional uses of the VHI as suggested by

Benninger and others is to assess measures after

treat-ment (1998) Murry and Rosen (2001) evaluated the

VHI in three groups of speakers to determine the

rela-tive severity of voice disorders in patients with muscular

tension dysphonia (MTD), benign vocal fold lesions

(polyps/cysts), and vocal fold paralysis prior to and

fol-lowing treatments Figure 1 shows that subjects with

vocal fold paralysis displayed the highest self-perception

of handicap both before and after treatment Subjects

with benign vocal fold lesions demonstrated the lowest

perception of handicap severity before and after

treat-ment It can be seen that in general, there was a 50%

or greater improvement in the mean VHI for the

com-bined groups However, the patients with vocal fold

paralysis initially began with the highest pretreatment

VHI and remained with the highest VHI after treatment

Although the VHI scores following treatment were

sig-niﬁcantly lower, there still remained a measure of

hand-icap in all subjects Overall, in 81% of the patients, there

was a perception of signiﬁcantly reduced voice handicap,

either because of surgery, voice therapy, or a tion of both

combina-The same investigators examined the application ofthe VHI to a speciﬁc group of patients with voice dis-orders, singers (Murry and Rosen, 2000) Singers areunique in that they often complain of problems relatedonly to their singing voice Murry and Rosen examined

73 professional and 33 nonprofessional singers andcompared them with a control group of 369 nonsingers.The mean VHI score for the 106 singers was 34.7,compared with a mean of 53.2 for the 336 nonsingers.The VHI signiﬁcantly separated singers from nonsingers

in terms of severity Moreover, the mean VHI score forthe professional singers was significantly lower (31.0 vs.43.2) than for the recreational singers Although lowerVHI scores were found in singers than in nonsingers, thisdoes not imply that the VHI is not a useful instrumentfor assessing voice problems in singers On the contrary,several questions were singled out as specifically sensi-tive to singers The findings of this study should alertclinicians that the use of the VHI points to the specificneeds as well as the seriousness of a singer’s handicap.Although the quality of voice may be mildly disordered,the voice handicap may be significant

Recently, Rosen and Murry (in press) presented liability data on a revised 10-question VHI The resultssuggest that a 10-question VHI produces is highly cor-related with the original VHI The 10-item questionnaireprovides a quick, reliable assessment of the patient’sperception of voice handicap

re-Other measures of voice outcome have been proposedand studied Recently, Gliklich, Glovsky, and Mont-gomery examined outcomes in patients with vocal foldparalysis (Hogikyan and Sethuraman, 1999) The in-strument, which contains ﬁve questions, is known as theVoice Outcome Survey (VOS) Overall reliability of theVOS was related to the subscales of the SF-36 for agroup of patients with unilateral vocal fold paralysis.Additional work has been done by Hogikyan (1999).These authors presented a measure of voice-relatedquality of life (VR-QOL) They also found that thisself-administered 10-question patient assessment of se-verity was related to changes in treatment Their sub-jects consisted primarily of unilateral vocal fold paralysispatients and showed a signiﬁcant change from pre- topost-treatment

A recent addition to functional assessment is theVoice Activity and Participation Proﬁle (VAPP) Thistool assesses the e¤ects voice disorders have on limitingand participating in activities which require use of thevoice (Ma and Yiu, 2001) Activity limitation refers toconstraints imposed on voice activities and participationrestriction refers to a reduction or avoidance of voiceactivities This 28-item tool examines ﬁve areas: self-perceived severity of the voice problem; e¤ect on the job;e¤ect on daily communication; e¤ect on social commi-nication; and e¤ect on emotion The VAPP has beenfound to be a reliable and valid assessment tool forassessing self-perceived voice severity as it relates toactivity and participation in vocal activities

Figure 1. Pre- and post-treatment voice handicap scores for

selected populations

Trang 37

The study of functional voice assessment to identify the

degree of handicap is novel for benign voice disorders

For many years, investigators have focused on acoustic

and aerodynamic measures of voice production to assess

change in voice following treatment These measures,

although extremely useful in understanding treatment

e‰cacy, have not shed signiﬁcant light on patients’

per-ception of their disorder Measures such as the VHI,

VOS, and VR-QOL have demonstrated that regardless

of age, sex, or disease type, the degree of handicap can

be identiﬁed Furthermore, treatment for these

handi-caps can also be assessed in terms of e¤ectiveness for the

patient Patients’ self-assessment of perceived severity

also allows investigators to make valid comparisons of

the impact of an intervention for patients who use their

voices in di¤erent environments and the patients’

per-ception of the treatment from a functional perspective

Assessment of voice based on a patient’s perceived

se-verity and the need to recover vocal function may be

the most appropriate manner to assess severity of voice

handicap

—Thomas Murry and Clark A Rosen

References

Adelstein, D J., Sharon, V M., Earle, A S., et al (1990)

Long-term results after chemoradiotherapy of locally

con-ﬁned squamous cell head and neck cancer American

Jour-nal of Clinical Oncology, 13, 440–447

Benninger, M S., Atiuja, A S., Gardner, G., and Grywalski,

C (1998) Assessing outcomes for dysphonic patients

Dejonckere, P H (2000) Perceptual and laboratory

assess-ment of dysphonia Otolaryngology Clinics of North

Amer-ica, 33, 33–34

Glicklich, R E., Glovsky, R M., Montgomery, W W (1999)

Validation of a voice outcome survey for unilateral vocal

fold paralysis Otolaryngology–Head and Neck Surgery,

120, 152–158

Hartl, D M., Hans, S., Vaissiere, J., Riquet, M., et al (2001)

Objective voice analysis after autologous fat injection for

unilateral vocal fold paralysis Annals of Otology,

Rhinol-ogy, and LaryngolRhinol-ogy, 110, 229–235

Hassan, S J., and Weymuller, E A (1993) Assessment of

quality of life in head and neck cancer patients Head and

Neck Surgery, 15, 485–494

Hogikyan, N D., and Sethuraman, G (1999) Validation of

an instrument to measure voice-related quality of life

(V-RQOL) Journal of Voice, 13, 557–559

Jacobson, B H., Johnson, A., Grywalski, C., et al (1998) The

Voice Handicap Index (VHI): Development and validation

Jacobson, G P., Ramadan, N M., Aggarwal, S., and

New-man, C W (1994) The development of the Henry Ford

Hospital Headache Disability Inventory (HDI) Neurology,

44, 837–842

List, M A., Ritter-Sterr, C., and Lansky, S B (1998) A

per-formance status scale for head and neck patients Cancer,

66, 564–569

Ma, E P., and Yiu, E M (2001) Voice activity and

partici-pation proﬁle: Assessing the impact of voice disorders on

daily activities Journal of Speech, Language, and HearingResearch, 44, 511–524

McHorney, C A., Ware, J E., Jr., Lu, J F., and Sherbourne,

C D (1993) The MOS 36-item short form health survey(SF-36): II Psychometric and clinical tests of validity inmeasuring physical and medical health constructs MedicalCare, 31, 247–263

Murry, T., Madassu, R., Martin, A., and Robbins, K T.(1998) Acute and chronic changes in swallowing and qual-ity of life following intraarterial chemoradiation for organpreservation in patients with advanced head and neck can-cer Head and Neck Surgery, 20, 31–37

Murry, T., and Rosen, C A (2001) Occupational voice orders and the voice handicap index In P Dejonckere(Ed.), Occupational voice disorders: Care and cure (pp 113–128) The Hague, the Netherlands: Kugler Publications.Murry, T., and Rosen, C A (2000) Voice Handicap Indexresults in singers Journal of Voice, 14, 370–377

dis-Newman, C., Weinstein, B., Jacobson, G., and Hug, G (1990).The hearing handicap inventory for adults: Psychometricadequacy and audiometric correlates Ear and Hearing, 11,430–433

Picarillo, J F (1994) Outcome research and otolaryngology.Otolaryngology–Head and Neck Surgery, 111, 764–769.Rosen, C A., and Murry, T (in press) The VHI 10: An out-come measure following voice disorder treatment Journal

of Voice

Rosen, C., Lombard, L E., and Murry, T (2000) Acoustic,aerodynamic and videostroboscopic features of bilateralvocal fold lesions Annals of Otology Rhinology and Lar-ynology, 109, 823–828

Smith, E., Lemke, J., Taylor, M., Kirchner, L., and Ho¤man,

H (1998) Frequency of voice problems among teachersand other occupations Journal of Voice, 12, 480–488.Wolfe, V., Fitch, J., and Martin, D (1997) Acoustic measures

of dysphonic severity across and within voice types FoliaPhoniatrica, 49, 292–299

World Health Organization (1980) International Classiﬁcation

of Impairments, Disabilities and Handicaps: A manual ofclassiﬁcation relating to the consequences of disease (pp 25–43) Geneva: World Health Organization

Electroglottographic Assessment of Voice

A number of instruments can be used to help ize the behavior of the glottis and vocal folds duringphonation The signals derived from these instrumentsare called glottographic waveforms or glottograms (Titzeand Talkin, 1981) Among the more common glotto-grams are those that track change in glottal flow, viainverse filtering; glottal width, via kymography; glottalarea, via photoglottography; and vocal fold movement,via ultrasonography (Baken and Orliko¤, 2000) Suchsignals can be used to obtain several di¤erent physio-logical measures, including the glottal open quotientand the maximum flow declination rate, both of whichare highly valuable in the assessment of vocal function.Unfortunately, the routine application of these tech-niques has been hampered by the cumbersome and time-consuming way in which these signals must be acquired,conditioned, and analyzed One glottographic method,

character-Electroglottographic Assessment of Voice 23

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electroglottography (EGG), has emerged as the most

commonly used technique, for several reasons: (1) it is

noninvasive, requiring no probe placement within the

vocal tract; (2) it is easy to acquire, alone or in

conjunc-tion with other speech signals; and (3) it o¤ers unique

information about the mucoundulatory behavior of the

vocal folds, which contemporary theory suggests is a

critical element in the assessment of voice production

Electroglottography (known as electrolaryngography

in the United Kingdom) is a plethysmographic technique

that entails ﬁxing a pair of surface electrodes to each side

of the neck at the thyroid lamina, approximating the

level of the vocal folds An imperceptible low-amplitude,

high-frequency current is then passed between these

electrodes Because of their electrolyte content, tissue

and body ﬂuids are relatively good conductors of

elec-tricity, whereas air is a particularly poor conductor

When the vocal folds separate, the current path is forced

to circumvent the glottal air space, decreasing e¤ective

voltage Contact between the vocal folds a¤ords a

con-duit through which current can take a more direct route

across the neck Electrical impedance is thus highest

when the current path must completely bypass an open

glottis and progressively decreases as greater contact

be-tween the vocal folds is achieved In this way, the voltage

across the neck is modulated by the contact of the vocal

folds, forming the basis of the EGG signal The glottal

region, however, is quite small compared with the total

region through which the current is ﬂowing In fact,

most of the changes in transcervical impedance are due to

strap muscle activity, laryngeal height variation induced

by respiration and articulation, and pulsatile blood

vol-ume changes Because increasing and decreasing vocal

fold contact has a relatively small e¤ect on the overall

impedance, the electroglottogram is both high-pass

ﬁl-tered to remove the far slower nonphonatory impedance

changes and ampliﬁed to boost the laryngeal

contribu-tion to the signal The result is a waveform—sometimes

designated Lx—that varies chieﬂy as a function of vocal

fold contact area (Gilbert, Potter, and Hoodin, 1984)

First proposed by Fabre in 1957 as a means to assess

laryngeal physiology, the clinical potential of EGG was

recognized by the mid-1960s Interest in EGG increased

in the 1970s as the importance of mucosal wave

dynam-ics for vocal fold vibration was conﬁrmed, and

accel-erated greatly in the 1980s with the advent of personal

computers and commercially available EGGs that were

technologically superior to previous instruments Today,

EGG has a worldwide reputation as a useful tool to

supplement the evaluation and treatment of vocal

pa-thology The clinical challenge, however, is that a valid

and reliable EGG assessment demands a ﬁrm

under-standing of normal vocal fold vibratory behavior along

with recognition of the speciﬁc capabilities and

limita-tions of the technique

Instead of a simple mediolateral oscillation, the vocal

folds engage in a quite complex undulatory movement

during phonation, such that their inferior margins

ap-proximate before the more superior margins make

con-tact Because EGG tracks e¤ective medial contact area,

the pattern of vocal fold vibration can be characterizedquite well (Fig 1) The contact pattern will vary as aconsequence of several factors, including bilateral vocalfold mass and tension, medial compression, and theanatomy and orientation of the medial surfaces Con-siderable research has been devoted to establishing theimportant features of the EGG and how they relate

to speciﬁc aspects of vocal fold status and behavior.Despite these e¤orts, however, the contact area function

is far from perfectly understood, especially in the face ofpathology Given the complexity of the ‘‘rolling andpeeling’’ motion of the glottal margins and the myriadpossibilities for abnormality of tissue structure or bio-mechanics, it is not surprising that e¤orts to formulatesimple rules relating abnormal details to speciﬁc pathol-ogies have not met with notable success In short, theclinical value of EGG rests in documenting the vibratoryconsequence of pathology rather than in diagnosing thepathology itself

Figure 1.At the top is shown a schematic representation of asingle cycle of vocal fold vibration viewed coronally (left) andsuperiorly (right) (after Hirano, 1981) Below it is a normalelectroglottogram depicting relative vocal fold contact area.The numbered points on the trace correspond approximately tothe points of the cycle depicted above The contact phases ofthe vibratory cycle are shown beneath the electroglottogram

Trang 39

Using multiple glottographic techniques, Baer,

Lo¨fqvist, and McGarr (1983) demonstrated that, for

normal modal-register phonation, the ‘‘depth of closure’’

was very shallow just before glottal opening and quite

deep soon after closure was initiated Most important,

they showed that the instant at which the glottis ﬁrst

appears occurs sometime before all contact is lost, and

that the instant of glottal closure occurs sometime after

the vocal folds ﬁrst make contact Thus, although the

EGG is sensitive to the depth of contact, it cannot be

used to determine the width, area, or shape of the glottis

For this reason, EGG is not a valid technique for the

measurement of glottal open time or, therefore, the open

quotient Likewise, since EGG does not specify which

parts of the vocal folds are in contact, it cannot be used

to measure glottal closed time, nor can it, without

addi-tional evidence, be used to determine whether maximal

vocal fold contact indeed represents complete

oblitera-tion of the glottal space Identifying the exact moment

when (and if ) all medial contact is lost has also proved

particularly problematic Once the vocal folds do lose

contact, however, it can no longer be assumed that the

EGG signal conveys any information whatsoever about

laryngeal behavior During such intervals, the signal

may vary solely as a function of the instrument’s

auto-matic gain control and ﬁltering (Rothenberg, 1981)

Although the EGG provides useful information only

about those parts of the vibratory cycle during which

there is some vocal fold contact, these characteristics

may provide important clinical insight, especially when

paired with videostroboscopy and other data traces

EGG, with its ability to demonstrate contact change in

both the horizontal and vertical planes, can quite

e¤ec-tively document the normal voice registers (Fig 2) as

well as abnormal and unstable modes of vibration (Fig

3) However, to qualitatively assess EGG wave

charac-teristics and to derive useful indices of vocal fold contact

behavior, it may be best to view the EGG in terms of

a vibratory cycle composed of a contact phase and a

minimal-contact phase (see Fig 1) The contact phase

includes intervals of increasing and decreasing contact,

whereas the peak represents maximal vocal fold contact

and, presumably, maximal glottal closure The

minimal-contact phase is that portion of the EGG wave during

which the vocal folds are probably not in contact Much

clinical misinterpretation can be avoided if no attempt

is made to equate the vibratory contact phase with the

glottal closed phase or the minimal-contact phase with

the glottal open phase

For the typical modal-register EGG, the contact

phase is asymmetrical; that is, the increase in contact

takes less time than the interval of decreasing contact

The degree of contact asymmetry is thought to vary not

only as a consequence of vocal fold tension but also as a

function of vertical mucosal convergence and dynamics

(i.e., phasing; Titze, 1990) A dimensionless ratio, the

contact index (CI), can be used to assess contact

sym-metry (Orliko¤, 1991) Deﬁned as the di¤erence between

the increasing and decreasing contact durations divided

by the duration of the contact phase, CI will vary

be-tween 1 for a contact phase maximally skewed to theleft andþ1 for a contact phase maximally skewed to theright For normal modal-register phonation, CI variesbetween 0.6 and 0.4 for both men and women, but,

as can be seen in Figure 2, it is markedly di¤erent forother voice registers Pulse-register EGGs typically haveCIs in the vicinity of0.8, whereas in falsetto it wouldnot be uncommon to have a CI that approximates zero,indicating a symmetrical or nearly symmetrical contactphase

Another EGG measure that is gaining some currency

in the clinical literature is the contact quotient (CQ).Deﬁned as the duration of the contact phase relative tothe period of the entire vibratory cycle, there is evidencefrom both in vivo testing and mathematical modeling tosuggest that CQ varies with the degree of medial com-pression of the vocal folds (see Fig 3) along a hypo-adducted ‘‘loose’’ (or ‘‘breathy’’) to a hyperadducted

‘‘tight’’ (or ‘‘pressed’’) phonatory continuum berg and Mahshie, 1988; Titze, 1990) Under typicalvocal circumstances, CQ is within the range of 40%–60%, and despite the propensity for a posterior glottal

(Rothen-Figure 2. Typical electroglottograms obtained from a normalman prolonging phonation in the low-frequency pulse,moderate-frequency modal, and high-frequency falsetto voiceregisters

Electroglottographic Assessment of Voice 25

Trang 40

chink in women, there does not seem to be a signiﬁcant

sex e¤ect This is probably due to the fact that EGG

(and thus the CQ) is insensitive to glottal gaps that are

not time varying Unlike men, however, women tend

to show an increase in CQ with vocal F0 It has been

conjectured that this may be the result of greater medial

compression employed by women at higher F0s that

serves to diminish the posterior glottal gap Nonetheless,

a strong relationship between CQ and vocal intensity has

been documented in both men and women, consistent

with the known relationship between vocal power and

the adductory presetting of the vocal folds Because

vocal intensity is also related to the rate of vocal fold

contact (Kakita, 1988), there have been some

prelimi-nary attempts to derive useful EGG measures of the

contact rise time

Because EGG is relatively una¤ected by vocal tract

resonance and turbulence noise (Orliko¤, 1995), it

al-lows evaluation of vocal fold behavior under conditions

not well-suited to other voice assessment techniques For

this reason, and because the EGG waveshape is a

rela-tively simple one, the EGG has found some success both

as a trigger signal for laryngeal videostroboscopy and as

a means to deﬁne and describe phonatory onset, o¤set,

intonation, voicing, and ﬂuency characteristics In fact,EGG has, for many, become the preferred means bywhich to measure vocal fundamental frequency and jitter

In summary, EGG provides an innocuous, forward, and convenient way to assess vocal fold vibra-tion through its ability to track the relative area ofcontact Although it does not supply valid informationabout the opening and closing of the glottis, the tech-nique a¤ords a unique perspective on vocal fold be-havior When conservatively interpreted, and whencombined with other tools of laryngeal evaluation, EGGcan substantially further the clinician’s understanding ofthe malfunctioning larynx and play an e¤ective role intherapeutics as well

straight-See also acoustic assessment of voice

—Robert F Orliko¤

References

Baer, T., Lo¨fqvist, A., and McGarr, N S (1983) Laryngealvibrations: A comparison between high-speed ﬁlming andglottographic techniques Journal of the Acoustical Society

of America, 73, 1304–1308

Baken, R J., and Orliko¤, R F (2000) Laryngeal function InClinical measurement of speech and voice (2nd ed., pp 394–451) San Diego, CA: Singular Publishing Group

Fabre, P (1957) Un proce´de´ e´lectrique percutane´ d’inscription

de l’accolement glottique au cours de la phonation: tographie de haute fre´quence Premiers resultats Bulletin del’Acade´mie Nationale de Me´decine, 141, 66–69

Glot-Gilbert, H R., Potter, C R., and Hoodin, R (1984) gograph as a measure of vocal fold contact area Journal ofSpeech and Hearing Research, 27, 178–182

Laryn-Hirano, M (1981) Clinical examination of voice New York:Springer-Verlag

Kakita, Y (1988) Simultaneous observation of the vibratorypattern, sound pressure, and airﬂow signals using a physicalmodel of the vocal folds In O Fujimura (Ed.), Vocalphysiology: Voice production, mechanisms, and functions(pp 207–218) New York: Raven Press

Orliko¤, R F (1991) Assessment of the dynamics of vocalfold contact from the electroglottogram: Data from normalmale subjects Journal of Speech and Hearing Research, 34,1066–1072

Orliko¤, R F (1995) Vocal stability and vocal tract ration: An acoustic and electroglottographic investigation.Journal of Voice, 9, 173–181

conﬁgu-Rothenberg, M (1981) Some relations between glottal air ﬂowand vocal fold contact area ASHA Reports, 11, 88–96.Rothenberg, M., and Mahshie, J J (1988) Monitoring vocalfold abduction through vocal fold contact area Journal ofSpeech and Hearing Research, 31, 338–351

Titze, I R (1990) Interpretation of the electroglottographicsignal Journal of Voice, 4, 1–9

Titze, I R., and Talkin, D (1981) Simulation and tion of glottographic waveforms ASHA Reports, 11, 48–55

interpreta-Further Readings

Abberton, E., and Fourcin, A J (1972) Laryngographicanalysis and intonation British Journal of Disorders ofCommunication, 7, 24–29

Baken, R J (1992) Electroglottography Journal of Voice, 6,98–110

Figure 3. Electroglottograms representing di¤erent abnormal

modes of vocal fold vibration

Tiêu đề	The MIT Encyclopedia of Communication Disorders
Trường học	Massachusetts Institute of Technology
Chuyên ngành	Communication Disorders
Thể loại	encyclopedia
Năm xuất bản	2003
Thành phố	Cambridge

Định dạng
Số trang	632
Dung lượng	8,75 MB