Speech and Voice Science

Third EdiTion

Speech and Voice Science

Third EdiTion

Alison Behrman, PhD, CCC-SLPWith Contributions By Donald Finan, PhD

5521 Ruffin RoadSan Diego, CA 92123

e-mail: info@pluralpublishing.comWebsite: http://www.pluralpublishing.com

Copyright © 2018 by Plural Publishing, Inc.

Typeset in 11/13 Garamond Book by Flanagan’s Publishing Services, Inc.Printed in the United States of America by McNaughton & Gunn

All rights, including that of translation, reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, recording, or otherwise, including photocopying, recording, taping, Web distribution, or information storage and retrieval systems without the prior written consent of the publisher.

For permission to use material from this text, contact us byTelephone: (866) 758-7251Fax: (888) 758-7255e-mail: permissions@pluralpublishing.com

Every attempt has been made to contact the copyright holders for material originally printed in another source. If any have been inadvertently overlooked, the publishers will gladly make the necessary arrangements at the first opportunity.

Library of Congress Cataloging-in-Publication Data

Names: Behrman, Alison, author. | Finan, Donald, author.Title: Speech and voice science / Alison Behrman with contributions by Donald Finan.Description: Third edition. | San Diego, CA : Plural, [2018] | Includes bibliographical references and index.Identifiers: LCCN 2017030922| ISBN 9781597569354 (alk. paper) | ISBN 1597569356 (alk. paper)Subjects: | MESH: Speech — physiology | Voice — physiology | Case ReportsClassification: LCC QP306 | NLM WV 501 | DDC 612.7/8 — dc23LC record available at https://lccn.loc.gov/2017030922

v

Contents

Preface to the Third Edition xiiiAcknowledgments xviAbout the Contributor xviiAbout the Illustrator xix

1 introduction 11.1 The Clinical Usefulness of Speech and Voice Science 2

Scenario 1 2Scenario 2 2Scenario 3 3

1.2 Defining Speech Science 31.3 Advice for Students on Effective Study Techniques 5

Study as Though You Are Having a Test Every Week 5Study With a Partner or Group 6Reach Beyond Memorization to Understand the Material 6Create Quizzes and Tests and Give Them to Yourself 7Stay Mindfully Present in Class 7Read Assignments Before and After Class 7Use the Study Aids 8

2 describing and Explaining Motion 92.1 Systems of Measurement 102.2 Describing Motion: Speed, Velocity, Acceleration, and Deceleration 112.3 Newton’s Laws Explain Motion 12

The First Law of Motion 12The Second Law of Motion 12The Third Law of Motion 12

2.4 Momentum and Energy 13Momentum 13Energy 14

Energy, Work, and Power 14Kinetic and Potential Energy 15

2.5 Three States of Matter 16Density 18Elasticity and Stiffness 19Pressure 21

Units of Measurement of Pressure 22References 23

vi Speech and Voice Science

3 Sound Waves 253.1 Vibration 263.2 The Nature of Waves 26

Pulse Waves 28Longitudinal Pressure Waves 28

3.3 Transfer of Energy in Waves 303.4 Visualizing a Sound Wave 333.5 Properties of Sound Waves 34

Frequency 34Period 36Intensity 37Wavelength 41

Speed of Sound 423.6 Pure and Complex Tones 43

Power Spectra 46Noise 48

3.7 Behavior of Sound Waves 49Interference 49Boundaries 51

Reflection 523.8 Resonance 52

Natural Resonant Frequency 53Standing Wave Patterns 55

Rules Governing Standing Waves 56Forced Vibration 58Acoustic Resonators 61

Recommended Internet Sites for Further Learning 62References 62

4 Breathing 63Clinical Case 1: Breath-Holding Speech 644.1 Introduction 654.2 Respiration 684.3 Balloons or Boyle’s Law? 684.4 Anatomy of the Lower Airway 70

The Work of Muscles 74Agonist-Antagonist Pairs 74Muscles and Levers 75

The Muscles of Breathing 764.5 The Biomechanics of Breathing 79

The Biomechanics of Tidal Breathing 79Lung Volumes and Capacities 83The Biomechanics of Forced Inhalation and Exhalation 85

4.6 The Biomechanics of Speech Breathing 86Relaxation Curve and Phonation 87Running Speech 89

Phrase Breath Groups 90

contentS vii

Adaptation of Speech Breathing to Variable Internal and External Demands 92Body Type 92Cognitive-Linguistic Variables 92Speech Breathing Personality 93Respiratory Demands 94

4.7 The Work of Breathing 96Airway Resistance 96Laminar and Turbulent Airflow 98Elastic Resistance 99Viscosity 100

4.8 Instrumentation for Measuring Breathing Kinematics 100Electromyography (EMG) 101Respiratory Inductance Plethysmography 102

Recommended Internet Sites for Further Learning 103References 103

5 Phonation i: Basic Voice Science 107Clinical Case 2: Running Out of Breath 1085.1 Overview 1095.2 Anatomy of the Larynx 109

Structural Framework 109Laryngeal Membranes and Cavities 111Three Functions of the Larynx 115Laryngeal Muscles 116

Intrinsic Muscles 116Extrinsic Muscles 121

The Vocal Folds 123Structural Overview 123Lamina Propria 124

Mechanical Layers 125Cricothyroid Joints 127Cricoarytenoid Joints 128Blood Supply to the Larynx and Lymphatic Drainage 129

5.3 Neural Control of Phonation 130Central Motor Control 130Peripheral Motor Neural Control and Brainstem Nuclei 130Peripheral Sensory Control and Brainstem Nuclei 133

5.4 Theories of Voice Production 133The Bernoulli Effect 135The Myoelastic-Aerodynamic Theory 138

5.5 Biomechanics of Vocal Fold Vibration 138Viscoelastic Component 141Vertical Phase Difference: The Mucosal Wave 142The Importance of Vocal Fold Closure 143Glottal Volume Velocity 144Laryngeal Airway Resistance 144Phonation Threshold Pressure 145Phonation Onset 146

viii Speech and Voice Science

5.6 Biomechanical Stress-Strain Properties of Vocal Fold Tissues 1485.7 Physiology of Phonatory Control 150

Fundamental Frequency (ƒo) 150Natural Resonance of the Vocal Folds 150Cover-Dominant Vibration 152Body Plus Cover Vibration 153Lung Pressure in the Regulation of ƒo 154Differential Control of ƒo: Evidence From EMG Data 155

Control of Intensity 156Auditory Feedback of Control of ƒo and Intensity 160

Biomechanical Forces During Phonation 1615.8 Voice Quality 162Recommended Internet Sites for Further Learning 163References 163

6 Phonation ii: Measurement and instrumentation 1716.1 Measurement of ƒo and Intensity 172

ƒo Measures 172Intensity Measures 174Voice Range Profile (VRP) 175

6.2 Measurement of Phonatory Aerodynamics 179Airflow and Lung Pressure 179

Vocal Efficiency 180S/Z Ratio 182Maximum Phonation Time 183Phonation Quotient 184

6.3 Instrumentation for Exploring the Dynamics of the Vocal Folds 184Stroboscopy 185High-Speed Laryngeal Imaging 188Videokymography (VKG) 188Photoglottography (PGG) 189Electroglottography (EGG) 191Open Quotient (OQ), Speed Quotient (SQ), and Contact Quotient (CQ) 193

6.4 Vocal Registers 195Modal Register 196Vocal Fry 196Falsetto 198

Recommended Internet Sites for Further Learning 199References 199

7 The Production and Perception of Vowels 207Clinical Case 3: Accent Management 2087.1 Introduction 2107.2 Acoustic Theory of Speech Production 211

Acoustic Characteristics of the Source 213The Vocal Tract Transfer Function 215Acoustic Characteristics of Lip Radiation 217Resonance and Standing Waves 218

contentS ix

7.3 Vowels 220Vocal Tract Constrictions and Formant Frequencies 221

First Formant Frequency (F1) 221Second Formant Frequency (F2) 222Third Formant Frequency (F3) 222

The Traditional Vowel Quadrilateral 222Vowel Quality and Articulatory Posture 225Acoustic Representation of Vowel Quality 226Resonating Cavities of the Vocal Tract 228Vowel Formant Normative Data 232Tense-Lax Vowel Quality and Inherent Duration 233Rhotacized Vowel Quality 234Diphthongs 235Intrinsic Pitch of Vowels 237

Tongue Anatomy 239Understanding Tongue Movements 241

7.4 The Vocal Tract as a Regulator of Intensity 243Harmonic Structure, Energy Loss, and Near-Periodicity 243Revisiting the Voice Range Profile 245

Singer’s Formant and Formant Tuning 246Speaker’s Formant 247

7.5 Acoustic Filters 2477.6 Instrumentation for Measuring Vocal Tract Acoustics 250

Sound Spectrography 250Narrowband and Wideband Spectrograms 251Exploring Spectrograms 252Nearly Periodic Voice Source 256Voiceprints: Voice Science or Science Fiction? 257

Quantitative Spectral Measures 257Long-Term Average Spectrum 257Harmonics to Noise Ratio 258Cepstral Measures 260

Inverse Filtering 2607.7 Vocal Tract Imaging: Current Research and Future Trends 261

Conventional Radiography (x-rays) 261Computed Tomography (CT) 262Magnetic Resonance Imaging (MRI) 263Ultrasound 267

Clinical Case 4: Ataxic Dysarthria 269Recommended Internet Sites for Further Learning 270References 270

8 The Production and Perception of Consonants 275Clinical Case 5: Facial Nerve Trauma 2768.1 Introduction 2778.2 Three Sources of Speech Sounds 280

Coarticulation 2818.3 Phonetic Description of Consonants 281

x Speech and Voice Science

Place of Articulation 281Manner of Articulation 282

8.4 Acoustic Representation of Consonants 283Stops 283

Stop Gap 283Release Burst 283Aspiration 285Voice Onset Time 286Formant Transitions 290Released and Unreleased Stops 294Glottal Stop 294

Fricatives 296Approximants 306

Glides (Semivowels) 307Liquids 309

Nasals 315Vowel Nasalization 319

Affricates 3198.5 Instrumentation and Measurement of Vocal Tract Aerodynamics 323

Intraoral Air Pressure 323Nasal Airflow and Acoustics 324

Nasal Airflow 324Nasalance 325

8.6 Instrumentation for Measuring Articulation 326X-ray Microbeam 326Electromagnetic Midsagittal Articulography (EMMA) 328Optoelectronic Tracking 329Strain Gauges 329Electropalatography 330

Clinical Case 6: Articulation Errors 332Recommended Internet Sites for Further Learning 332References 333

9 Prosody 339Clinical Case 7: Parkinson’s Disease 3409.1 Introduction to Prosody 3419.2 Basic Building Blocks of Prosody 342

Intonation (ƒo Contour) 342Timing (Duration and Juncture) 345Loudness (Intensity Contour) 347

9.3 Syllabic Stress and Prominence 3489.4 Speech Rhythm 352

Temporal Measurements of Rhythm 3539.5 In Summary of Prosody 354References 355

10 Theories and Models of Speech Production 35910.1 Introduction 361

contentS xi

10.2 Theories and Models 36310.3 Theoretical Issues for Consideration 365

Degrees of Freedom 365Output Targets 366Motor Programs 368Dynamic Systems 368Serial Ordering and Sensory Feedback 368Spatiotemporal Organization 370Unit of Analysis 372Coarticulation 378

Motor Planning: How Far Ahead? 378Frame Theory 379Hybrid Model 381

10.4 Investigational Considerations 382Speaking Task 382Perturbation Studies 383Rate 384

10.5 Influences From Connectionist Models 38610.6 Language and Speech 387Recommended Internet Sites for Further Learning 388References 390

11 Theories of Speech Perception 39911.1 Introduction 40011.2 The Perception of Sound Waves 400

Perception of Intensity 400Perception of Frequency 402

11.3 Topics in Speech Perception 403Lack of Invariance 403Unit of Analysis Revisited 405Lack of Segmentation 405Perceptual Normalization 405Specialized Perception of Speech 406

Duplex Perception 407The McGurk Effect 407

Contextual Effect 40811.4 Theories of Speech Perception 408

Motor Theory 410Direct-Realist Theory 410Native Language Magnet Theory 411Acoustic Landmarks and Distinctive Features 411TRACE 412The Cohort Theory 412

11.5 What Babies Can Tell Us About Perception 413Recommended Internet Sites for Further Learning 415References 415

xii Speech and Voice Science

12 instrumentation 421 Donald Finan 42112.1 Introduction to Measurement 42212.2 Basic Principles of Measurement 422

Error in Measurement 424Transduction 425It’s Electric! 427

12.3 Sensors for Capturing Speech 42712.4 Microphones 429

Microphone Designs 429Microphone Transducer Types 430Microphone Performance Characteristics 431

Directionality 431Frequency Response 432Sensitivity and Dynamic Range 433Adequate Microphone Performance for Speech Analysis 434

12.5 Amplification 436Amplifier Performance Characteristics 436

Gain 436Frequency Response 437Dynamic Range 437

Amplifier Compatibility 43812.6 Making the Connection 43912.7 Recording Environment 440

Ambient Acoustic Noise 441Electromagnetic Interference 441

12.8 Data Acquisition: Let’s Get Digital 442Sampling: Time Representation 443Quantization: Amplitude Representation 446

Frequency-Based Error: Aliasing 446Amplitude-Based Error: Quantization Noise and Peak Clipping 447

12.9 Data Storage 44812.10 Balancing Cost, Complexity, and Accuracy in Digital Data Acquisition 45012.11 Best Practices for the Use of Instrumentation 453

Sensor Performance and Use 453Preamplifier Performance and Use 455Data Acquisition System Performance and Use 456

12.12 Let’s Wrap This Thing Up! 456References 456

Appendix A. Measurement Conversions 459Appendix B. Reading Passages 461Appendix C. Frequencies of the Musical Scale 467Appendix D. The International Phonetic Alphabet 469

Index 471

xiii

Preface to the Third Edition

I have three distinct, yet interwoven, professional roles: teacher, research scientist, and clinician. This book grew out of my clinical practice. How odd, you might think, for this book is a basic sci-ence textbook written primarily for students of speech-language pathology. The role of teacher or research scientist would appear to be a more likely candidate as motivation for this book. Yet I have been struck constantly by the realiza-tion of principles of physics and physiology in my interactions with my patients. In truth, the answers for many of the clinical questions raised by speech-language pathologists can be found in the science of voice and speech production and perception. How does one address a defi-cit in a voice- or speech-disordered individual? Why does a therapeutic technique work for one patient and not for another?

In sum, a solid grounding in speech science makes a speech-language pathologist a better clini-cian. This book was motivated by my desire to pro-vide students of speech-language pathology with a strong fund of knowledge in speech science — so that they would have this part of the necessary tools with which to become outstanding clinicians and so that they, too, could experience the delightful process of clinical inquiry, problem solving, and, yes, clinical creativity. For it is only with a fund of knowledge larger than the moment — greater than one accesses on a day-to-day basis — that one can truly have the freedom to be creative in therapeu-tic approaches and techniques.

This book is intended primarily for under-graduate and graduate students in speech-language pathology. It should also be of interest to doctoral students and to research scientists as a basic reference text. It is my hope that sea-soned clinicians, too, will find this book valu-able as a reference source when they encounter patients with speech and voice disorders that present therapeutic challenges.

This book addresses the physics, acoustics, and physiology of voice and speech production. An effort is made to provide a sense of history (remote and recent) and, thereby, a sense of the future direction of the field. I have tried to incor-porate some interesting and even amusing notes in the shorter side boxes to help lighten some of the admittedly dense material. Other side boxes are central to understanding the content of the chapter. Printed textbooks remain quite linear in their presentation of material. Most college students, however, have become acclimated to the nonlinear information-gathering style of the Internet, and so I suspect that they will enjoy the side boxes without finding them distracting.

new to the Third Edition

Some exciting new changes have been made to this third edition. Clinical cases, with discussion questions, have been added at the beginning of Chapters 4, 5, 7, 8, and 9 and two more at the end of Chapters 7 and 8. These cases serve to emphasize to the student the clinical utility of speech and voice science and to stimulate thinking and, hopefully, some lively classroom (in-person or virtual) discussions. Discussion questions are provided at the end of each clinical case. Although each clinical case focuses upon the content of the chapter in which it occurs, information is also drawn from other chapters, with some of the discussion questions address-ing topics of other chapters. Thus, instructors may find it useful to help the students reexamine each clinical case in subsequent chapters.

Two new chapters have been added to this third edition. Don Finan has provided a much-needed chapter on instrumentation (Chapter 12). It covers basic information about digital signal

xiv Speech and Voice Science

processing, the instrumental array, consideration of instrumental specifications, and how to obtain valid and reliable acoustic and biophysical data. It demystifies the data acquisition process while, hopefully, stimulating students to try their hand at data gathering themselves.

A new chapter on prosody (Chapter 9) has been added in response to growing interest in prosodic differences among speakers with dif-ferent native language backgrounds, as well as prosodic disturbances associated with disease processes. Some of the information contained in that chapter had previously been located at the end of the chapter on consonants. Now in its own chapter, coverage of prosody has been expanded to include the acoustic properties that contribute to stress, prominence, and speech rhythm, and its clinical relevance is highlighted.

New to this third edition is the use of the PluralPlus companion website. For students, material includes study aids such as key terms and review questions for each chapter (except for Chapter 1) and a speech science version of a game called Taboo — a lighthearted way to help students study. After all, speech science should be fun (at least a little). For instructors, sugges-tions for classroom learning activities and lab assignments using free, downloadable acoustic analysis software are offered to provide more effective learning experiences for both under-graduate and graduate students. Revised and updated slides are provided for traditional class-room lectures, and responses to the clinical case questions are provided to help guide classroom discussions or testing.

Reorganization of the introductory material provides a new chapter (Chapter 2) on the phys-ics of motion. This chapter appeared in the first edition and then mysteriously disappeared in the second addition. It has been brought back due to popular demand.

how to Use This Book

The curriculum for speech and voice science varies considerably at the undergraduate and graduate levels across university programs. As

such, this book offers some flexibility for fac-ulty. The order of the chapters is organized for a full course in undergraduate speech science. The basic physics of sound (Chapters 2 and 3) lays the groundwork for the students’ understand-ing of speech and voice production. Subsequent chapters mirror somewhat the process of speech production — the respiratory, phonatory, resona-tory, and articulatory subsystems (Chapters 3 through 8) — and the interplay of those subsys-tems in prosody (Chapter 9). Once the students have that basic understanding of speech and voice production, they are ready to ponder the theories of speech production and perception (Chapters 10 and 11).

The chapters on voice production (Chap-ter 5 and 6) are quite in-depth, and the content may be beyond what some instructors need for (or have time in) an undergraduate course in speech science. The chapters are designed such that the more advanced information on phona-tory biomechanics and measurement can easily be omitted. And these two chapters work well as part of the curriculum of a graduate-level course in voice disorders.

Don Finan’s excellent new chapter on instru-mentation (Chapter 12) can be used in several ways. Some instructors may want to cover this chapter early in the semester, after Chapters 2 and 3, to prepare students for discussion of the instrumentation sections at the end of Chap-ters 4 through 8. Other instructors may prefer to address the topic in the order in which it is presented in the book, so that students have a basic knowledge of speech and voice produc-tion within which to explore the gathering of instrumental data. The chapter was written to work well with either of these approaches. The chapter also stands well on its own as a refer-ence for graduate- and doctoral-level students who are conducting research.

Chapters 4, 5, 7, and 8 each contain a short review of the relevant anatomy. It is presumed that students will have taken a course in anatomy and physiology of the speech mechanism or are taking that course concomitant with speech sci-ence. Therefore, here, the anatomy is presented as a refresher for students and for easy refer-

3. Sound WaVeS xv

ence, rather than at a level of detail expected for novel learning of the material. The anatomy sections also serve to highlight some important anatomical features that prepare the students for the subsequent speech and voice science topics.

For Chapters 1 through 11, I have used “we” throughout this book in lieu of “I” even though the chapters were largely sole authored. The rea-son for the plural pronoun is that the knowledge and authority with which I wrote those chapters

is drawn from a legion of speech and voice sci-entists who have contributed the vast amount of data upon which this book is based. They have done all the good cooking. I am just carrying it to the table.

As always, I welcome comments, criticisms, and suggestions for changes to future editions to keep this textbook as useful as possible for instructors and students. You can find me at Alison.Behrman@lehman.cuny.edu

xvi

Acknowledgments

Many individuals contributed to the creation of the three editions of this textbook, and with-out them this project would never have come to fruition. I am quite indebted to the following people:

To Donald Finan, who contributed a fabulous chapter on instrumentation to this third edition.

To Maury Aaseng, whose delightful illustrations bring alive the book.

To Andrew Pancila, who revised the spectrograms in Chapter 8 to make them more legible for this third edition.

To Karen J. Kushla, who provided helpful editing on some of the hearing science topics in Chapters 3 and 11.

To Philip Doyle, James and Zaida McDonough, and Sarah Sheridan, whose thoughtful commentary on the first edition made this book more readable.

To my students across the years, who inspire and teach me, perhaps more than I teach them.

And a large thank you to the Plural Publishing family (some of whom, sadly, are no longer with us): Angie and Sadanand Singh, Sandy Doyle, Valerie Johns, Kalie Koscielak, and Linda Shapiro.

xvii

About the Contributor

Donald Finan, PhD, is a Professor in the Audi-ology and Speech-Language Sciences program at the University of Northern Colorado. He is a speech scientist with a background that encom-passes speech-language pathology and audi-ology, speech physiology, neuroscience, and instrumentation. His research interests include the measurement of noise in relation to auditory exposure, normal speech motor control over the lifespan, the use of technology in clinical and research settings, and the development of original tools and pedagogies for speech science instruction. Dr. Finan is the co-developer of the

innovative course Musical Acoustics and Health Issues taught at the University of Northern Colo-rado. In this course, students explore acoustics by constructing cigar box guitars and PVC pipe didgeridoos, among other hands-on projects related to the speech and hearing sciences. Dr. Finan is the inaugural Coordinator of ASHA’s Special Interest Group 19, Speech Science, and he moderates the Facebook page “Speech Sci-ence Toolbox” (https://www.facebook.com/SpeechScienceToolbox/) where resources for teaching speech science are shared.

xix

About the illustrator

Maury Aaseng received his degree in Graphic Design from the University of Minnesota, Duluth, with an emphasis on illustration in design. Before graduation, a semester in Australia allowed him to focus on exotic wildlife illustration. He now lives in San Diego, where he illustrates full time. He has created images for a variety of book topics, such as diseases, nature, inventors, forensics, and speech pathology*. In addition to book illustration, he makes custom paintings and is a member of the Southern California Cartoonists Society. His many trips to the San Diego Zoo have been the inspiration behind his zoo- themed comic strip, Nolan’s Ark.

Aaseng enjoys spending his time outdoors, and is an enthusiastic naturalist. Drawing and a love of animals developed into passions during his childhood in Wisconsin. Frequent camping trips into the California countryside have continued to fuel both interests. His other hobbies include SCUBA and snorkeling, bowling, reading, and biking.

* Note: This is definitely the first book he’s illustrated such complex ideas as a punk rocker’s tongue, a pig talking on a cell phone, and the uncontrollable, maddening craving for toast.

Mr. Watson - come here - I want to see you. The first audible words spoken over the telephone.

—alexander graham bell, Scottish inventor of the telephone and audiometer, among many

other inventions (1847–1922)

3Sound Waves

If a tree falls in a forest andno one is around to hear itfall, does it make a sound?

Figure 3–1. if a tree falls in a forest and no one is around to hear it fall, does it make a sound?

26 Speech and Voice Science

Does a tree falling in the forest create a sound if no one is around to hear it fall? We shall leave that oft-debated question to the philosophy classes; however, as speech-language patholo-gists, we will define sound as a pressure wave that is audible to the human ear with normal auditory sensitivity. The nature of that pressure wave, its production and perception, are the heart of the content of this textbook and, indeed, the heart of clinical speech-language pathology. And so the sound wave bears closer examination.

3.1 Vibration

What is vibration? At its most simple, vibration (oscillation) is a back-and-forth motion. Pretend you have a small ball attached to a spring sus-pended from a bar. The ball has a certain mass (a measure of the quantity of its matter), and we refer to this setup as a mass-spring system. Initially, the ball will stretch the spring to a point where it will sit quietly at rest, suspended on the spring. The ball-spring system is then said to be at equilibrium. When not disturbed by an outside force, the ball will maintain this rest position. We know this fact because Newton’s first law of motion tells us so. If the spring is dis-torted by some agent pulling it downward and then releasing it, the mass and spring will imme-diately recoil upward. Why? Because Newton’s third law of motion tells us that a force will act upon the system equally and opposite to the ini-tial downward distortion. The potential energy that is built up in the system by the downward pull will be released as kinetic energy in the upward movement. The force that causes the mass-spring system to be restored to its prior, undistorted position is called a restorative force. The initial force that caused the mass-spring sys-tem to move from its position of equilibrium can be referred to as a displacement force. When the system is undisturbed at rest, it is at equilibrium, which means that the net restoring forces acting upon it are zero. The greater the displacement force, the greater proportionately the restorative force. Stretch the spring a little and the force that acts to restore the mass to equilibrium is

small. Displace the spring a great deal, and the restorative force is large. (Displace the mass too much and the spring breaks — a special situation we will ignore.)

Now we know that if the mass is displaced by pulling on the spring, it will not simply move back to its initial rest position and stop. If an object is distorted and then released, elastic restorative forces accelerate the mass upward toward its equilibrium position (Figure 3–2). As the mass approaches equilibrium, the net restoring force decreases, and eventually when the mass reaches equilibrium, the net restoring force is zero. But why does the mass not stop at that point? Why does it maintain its upward trajectory? Inertial forces cause the mass to con-tinue moving upward. Remember that inertia is the tendency of an object to resist change in movement. And we know that the momentum of an object is a product of its mass and accelera-tion. Thus, inertia causes the mass to overshoot the equilibrium position and continue moving upward. As the mass continues to overshoot equilibrium (that is, the negative displacement is increasing), the restorative force increases. The increasing restorative force acts to slow the upward movement of the mass — the restorative force acts to decelerate the mass. Finally, it stops at its topmost point and is pulled back toward equilibrium. However, the inertia of the dis-placed mass causes it to overshoot the rest posi-tion and distort in the opposite direction. Again, elastic restorative forces cause the mass to return to its original position. And again, the inertia of this second displacement causes the object to overshoot the rest position and distort in the initial direction. This cycle of vibration continues to repeat itself. However, frictional forces (forces that oppose movement) will cause the vibration to lose energy with each cycle, unless an outside force provides energy, and eventually the mass will stay in its rest position (Figure 3–3).

3.2 The nature of Waves

Speech is composed of sound waves, which is why we spend so much time studying waves.

3. Sound WaVeS 27

Waves are all around us, more ubiquitous prob-ably than most people realize. Waves are com-posed of vibrations that move energy from Point A to Point B without actually moving an object or material from A to B. How is this so?

Waves are created by a disturbance. A wave is a disturbance that travels through a medium, transporting energy from one location to another. The medium is the material through which the wave passes; it is that which carries or transports the wave. Throwing a stone into a pond causes waves. The stone (and the force with which it has been thrown) is the disturbance, and the

medium that transports the disturbance is water. The medium is simply a series of interconnected particles that interact with one another. The par-ticles of the water wave are the water molecules. Say hello to your friend and your friend hears you because of the sound wave you produced. Your vocal folds created the disturbance (much more about that later). The medium that transports the disturbance is air. The particles of air that interact with one another to carry the energy of your “hello” to your friend are the air molecules. In old-time western movies, the cowboy would put his ear against the railroad track to feel for

Newton's 1 Lawst Newton's 3 Lawrd

Potential Energy

Equilibrium

Kinetic Energy

Restorative Force

ElasticRestorativeForce

Due to outside forceDue to inertia & momentum

DisplacementForce

1

2

DisplacementForce1

2

Figure 3–2. a description of vibration.

Equilibrium

Overshoot

Figure 3–3. Frictional forces will cause the vibration to lose

energy with each cycle, unless an outside force provides energy, and eventually the mass will stay in its

rest position.

282 Speech and Voice Science

bilabials are produced with both lips coming together to occlude the airway, as in /p, b, m/. The labiodental consonants are produced with the lower lip against the upper front teeth, as in /f, v/. The dental consonants are produced with the tongue tip or tongue blade against the upper front teeth, as in the sounds /θ, ð/. The alveo-lar consonants are produced with the tongue blade against the back of the alveolar ridge, as in /t, d/. Some speakers place the tip of the tongue behind the lower front teeth and others place it up near the alveolar ridge. However, the tongue blade is always placed at or behind the alveo-lar ridge for alveolar sounds. Palatal consonants are produced with the tongue blade against the hard palate, as in the sound /ʃ, ŋ, j/. Velar conso-nants are produced with the back of the tongue against the soft palate, as in /k, g/. The retroflex consonant /r/ can be produced with the back of the tongue against the alveolar ridge. A signifi-cant amount of variability, however, exists with the retroflex sound among different speakers. American English has only one pharyngeal frica-

tive, the /h/, which is sometimes classified as a glottal sound.

Manner of Articulation

The manner of articulation refers to the degree of constriction in the vocal tract and its effect upon the airflow. The constriction may be tran-siently complete, in which case the airflow is fully stopped momentarily, such as occurs for stops (synonymously, plosives, in American English) and affricates. The constriction may be incomplete, such that the airflow is impeded to a greater or lesser extent, either for a short dura-tion or for a relatively long period (long relative to the production of phonemes within running speech). When the constriction is incomplete and airflow continues, the consonant is said to be a continuant. The continuants include frica-tives, glides, liquids, and nasals. Table 8–1 lists the consonants of American English by place, manner of articulation, and voicing.

Table 8–1. the consonants of american english, organized by Manner and place of articulation and presence (+V) or absence (−V) of Voicing

Labial Labiodental dental Alveolar Palatal VelarPharyngeal or Glottal

−V +V −V +V −V +V −V +V −V +V −V +V −V +V

Stops p b t d k g

Fricatives f v θ ð s z ʃ Z h

affricates tʃ dZ ŋ

nasals m n

Liquids lateral

l

Liquid retroflex

r

glides (semi-vowels)

w j

8. the production and perception oF conSonantS 283

Study Questions

1. Distinguish an upstream constriction from a downstream constriction in the vocal tract.

2. Identify the three sources of speech sounds and the types of sound waves generated by these sources.

3. Define anticipatory and retentive coarticulation.

4 Traditionally, consonants are identi-fied by three features. Name them.

5. What are the articulatory points of contact that identify place of articu-lation? Provide an example of each. Which points specify tongue contact and which do not?

6. To what does manner of articula-tion refer? List the seven manners of articulation and provide an example of each.

7. Which manners of articulation are considered continuants? Why?

8.4 Acoustic representation of Consonants

Stops

In the stop, or plosive, a complete constriction of the vocal tract occurs, causing cessation of the airflow. Upon release of the constriction, the airflow resumes in a burst of sound. (Think of an explosion of escaping air; hence “plosive.”) The bilabial, alveolar, and velar stops, in the voice-less and voiced cognate pairs, are /p, b/, /t, d/ and /k, g/, respectively (Figures 8–4 and 8–5). The stop consonants are complex sounds with many allophonic variations. No single, invariant

(always present) set of acoustic features exists to alert the listener to stop production. Four acous-tic cues are important for perception of the stop: the silence, the burst noise, the voice onset time, and the poststop vowel formant transition. These features are each discussed below.

Stop Gap

Silence, also called the stop gap, occurs dur-ing production of the plosive prior to release of the airflow (Figures 8–4, 8–5, and 8–6). For the voiceless stops /p, t, k /, complete silence occurs momentarily. For the voiced stops /b, d, g/, vocal fold vibration may continue through part or all of the stop, producing a low-amplitude sound. Recall from Chapter 4 that vocal fold vibration can occur only in the presence of a transglottal pressure drop. On complete closure of the vocal tract during stop production, the supraglottal pressure will quickly equilibrate to the lung pressure, at which time phonation will cease. During running speech, the duration of the voiced stop is often short enough that the supraglottal pressure never reaches the same level as the lung pressure. In that case, the voic-ing continues throughout the closed portion of the voiced stop. In other cases, however, pres-sure equilibration occurs and the voicing ceases prior to release of the stop. The presence of voic-ing during the closed portion often is referred to as the voice bar, as indicated in the spectrogram in Figure 8–5. The voiced sound produced dur-ing the closed portion of the stop, however, is substantially damped by the vocal tract, and so it is a low-energy, soft sound. The waveforms in Figures 8–4 through 8–6 show the low-ampli-tude sound pressure corresponding in time to the voice bar in the spectrogram.

Release Burst

A brief transient burst noise occurs upon release of the occlusion and the impounded air. (This is the “pop” sound you often hear when some-one is speaking into a microphone and has held the microphone too close to the mouth.) During

284

Waveform

/ɛ/ /p/ /ɛ/ /ɛ/ /t/ /ɛ/ /ɛ/ /k/ /ɛ/

Wideband spectrogram

burst

aspiration

stop gap aspiration

stop gap

F1

F2

F3

Am

plit

ude

Frequency

Figure 8–4. acoustic features of the voiceless stops.

Waveform

Wideband spectrogram

/ɛ/ /b/ /ɛ/ /ɛ/ /d/ /ɛ/ /ɛ/ /g/ /ɛ/

burst

burst

voice bar

F1

F2F3

stop gapaspiration

Frequency

Am

plit

ude

Figure 8–5. acoustic features of the voiced stops.

I’ve always felt, even as a songwriter, that the rhythm of speech is in itself a language for me.

— cyndi Lauper, american singer-songwriter (1953– )

9Prosody

How dare you

text me in that

tone of voice!

Figure 9–1

340 Speech and Voice Science

Clinical Case 7: Parkinson’s disease

Clinical cases are based upon real patients whom the author has treated. Evaluation and treatment information has been edited to focus upon specific features related to the chapters. Note that clinical cases incorporate informa-tion that is covered in this and other chapters (and some information about diagnosis and therapy that you will learn in future courses). You are encouraged to review this case before you begin your study of this chapter and once again after you have completed the chapter. You may also want to revisit this case later in the semester after you have covered additional chapters.

cheung is a 74-year-old retired lawyer. he is fully bilingual (Mandarin/english), having specialized in international chinese american import-export law. he speaks in both Manda-rin and english with his wife and adult sons. he is trying to teach his two grandchildren Mandarin, although they don’t show much interest in learning it. cheung was diagnosed with parkinson’s disease 2 years ago, a neu-rological disorder of the basal ganglia that causes tremors, rigidity, slowness of move-ment, and impaired sensory (and often cog-nitive) perception. he takes medication to control the symptoms, and he participates in daily physical activity (walking, riding a sta-tionary bicycle), as recommended by his neu-rologist, to maintain flexibility and strength. however, recently his wife and children have complained that his speech is difficult to understand and that he mumbles and speaks too quietly. cheung’s wife reported that his speech in Mandarin was even harder to under-stand than his english, which she attributed to his lack of tone variation. (Mandarin is a tonal language and therefore variation in tone is essential to meaning.) cheung’s neurologist recommended a speech-voice evaluation and therapy to minimize the effects of parkinson’s disease on cheung’s speech and to maintain maximum intelligibility.

the speech-voice evaluation revealed consistently reduced intensity, delayed onset of utterances within conversational context, reduced articulatory precision, and exces-sive coarticulation. prosody was moderately impaired, with decreased ƒo and intensity contours, and decreased phrasal prominence. Speech rhythm was characterized by increas-ing rate of speech over the course of an utter-ance, with increased pause time at phrase endings. upon questioning, cheung denied speech problems and attributed his wife and children’s complaints to lack of effort to listen carefully to him. overall, speech intelligibility was moderately impaired. Stimulability testing for increased intensity and prosodic variation revealed small improvement, but significant cueing was required.

the SLp conducting the evaluation knew that cheung’s speech deficits were charac-teristic of people with parkinson’s disease. denial of speech problems was also a com-mon occurrence associated with the neuro-logical deficits of the disease. a course of speech-voice therapy was initiated, focusing upon increased speech intensity and articula-tory precision and decreased rate of speech, together with increasing cheung’s awareness of the need to use significantly greater effort to speak loudly and clearly. increased depth of preutterance inhalation and increased open-ing of the mouth during speech were used to help cheung increase speech intensity. to help cheung improve his prosody in english, the SLp prepared phrases that were relevant to his daily activities and asked him to select the most important word in the phrase and then use greater intensity for that word, even while maintaining increased intensity for the entire phrase. (in other words, speaking loudly for the whole phrase and even louder for the most important word.) the SLp did not know Manda-rin. however, to help him increase his intelligi-bility in Mandarin, he invited cheung’s wife to

9. proSodY 341

9.1 introduction to Prosody

Email and text are efficient methods of commu-nication — most of the time. But we have all had the experience of being misinterpreted in both media. Humor, sarcasm, anomalous sentences, and subtleties of interpretation are difficult to transmit to the “listener” because we commu-nicate these features beyond the phonetic level of written characters. Thus, we often resort to emoticons, the pictorial representation of a facial expression, such as the happy face or punctua-tion such as :). Emoticons represent not only facial expression, however; they also represent, although not always effectively, the expressive-ness in our speech that transmits our intent. Such expressiveness is the topic of prosody.

The vowels and consonants that we have been considering over the course of the previous chapters are speech segments, which form the nuclei and boundaries of syllables. The syllables, in turn, are grouped together to build an utter-ance. The utterance can be composed of a single syllable (as in “No!”) or a longer grouping that comprises a fully grammatical sentence. From an acoustic viewpoint, the meaning of the utter-ance is communicated at two broad levels. One level is the phoneme, the smallest meaningful segment, and the coarticulation of combinations

of phonemes. The other level of meaning is car-ried by features that are superimposed upon the segments. In other words, the intent of the utter-ance is communicated both at the segmental and the suprasegmental level. The suprasegmental level or, synonymously, prosody is defined by Sanderman and Collier (1996) as “the ensemble of phonetic properties that do not enter into the definition of individual speech sounds” (p. 321). For ease of reference throughout this chapter, we use the term prosody.

The segmental features of vowels and con-sonants discussed in Chapters 7 and 8 are inher-ent characteristics of the phonemes, either in isolation or due to coarticulatory effects. Pro-sodic features, in contrast, are defined by their relative values to one another. For example, the segmental acoustic feature of voice onset time for /bit/ can be measured meaningfully with-out reference to the voice onset time of another voiced plosive. In contrast, the meaning, or com-municative function, of the amount of stress (a prosodic feature we have yet to define) that the speaker places upon the plosive, as in, “I said beet, not Pete!” can be interpreted mean-ingfully only in comparison to another segment within the phrase. In this chapter, we consider the ways in which meaning is communicated through prosody and the acoustic manifestation of prosody.

participate in the therapy. using a list of Man-darin words, cheung was instructed to exag-gerate tonal changes, while his wife reported on the accuracy of the words. after 1 month of twice-weekly therapy, cheung demonstrated significantly increased self-monitoring skills, and his wife and children reported that his speech was significantly easier to understand in both languages.

Clinical Case Discussion Questions

1. What key features of prosody did the SLp address with cheung in Mandarin and

english? Which prosodic features were not addressed?

2. explain the differences in the prosody approach used by the SLp for Mandarin and english. (be aware of the difference between ƒo contour, word stress, and phrase prominence.)

3. What is the relationship between inten-sity, increased depth of inhalation, and increased mouth opening (see chapters 5 and 7)?

4. how is the acoustic theory of speech pro-duction relevant to cheung’s speech-voice deficit?