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Date: Fri, 9 May 2003 13:01:24 -0400 (EDT) From: Chao-Yang Lee Subject: Acoustic & Auditory Phonetics, 2nd ed.
Johnson, Keith (2003). Acoustic and Auditory Phonetics, 2nd ed., Blackwell Publishing.
Chao-Yang Lee, Speech Communication Group, Research Laboratory of Electronics, Massachusetts Institute of Technology
This book is a non-technical introduction to the acoustics of speech. As the author notes, it covers four major topics: (1) acoustic properties of major classes of speech sounds, (2) the acoustic theory of speech production, (3) the auditory representation of speech and (4) speech perception.
The target audience is students in introductory courses in linguistic phonetics, speech and hearing science, and in branches of electrical engineering and cognitive psychology that deal with speech.
The nine chapters are divided into two parts. The first part presents the theoretical foundation and signal processing tools for the study of speech sounds. Chapter 1, basic acoustics and acoustic filters, introduces the physics of sound: sound propagation, sound waves, graphical representations of sound, and characteristics of acoustic filters. Chapter 2 reviews fundamentals of digital signal processing, explicating how the analog speech signal is converted to digital form for various types of speech analysis. Chapter 3 discusses the basics of audition, including the anatomy of the peripheral auditory system, the sensation of loudness and pitch, and the difference between acoustic and auditory representations of sound. Chapter 4 on speech perception is new to the second edition. It illustrates how a speech perception experiment is conducted by evaluating the perceptual distance among speech sounds. The role of linguistic background on speech perception is also demonstrated by a study on Mandarin tone perception.
Chapter 5, the acoustic theory of speech production, lays the theoretical foundation for subsequent discussions on the acoustics of major classes of speech sounds. The voice source and its acoustic properties, such as fundamental frequency and harmonics, are first introduced, followed by a discussion on the filtering function of the vocal tract and its acoustic consequences. The calculation of resonant frequencies modeled by simple tubes is discussed, so is the estimation of vowel formant frequencies via the linear predictive coding (LPC).
Based on the acoustic theory presented in Chapter 5, the second part of the book explicates the acoustic, auditory, and perceptual characteristics of the major classes of speech sounds. Chapter 6 presents the acoustics of vowels modeled by tubes and by the perturbation theory. The distribution of vowels in the acoustic vowel space is discussed with reference to the quantal theory by Stevens and the theory of adaptive dispersion by Lindblom. The auditory representation of vowels is compared to the acoustic representation, followed by a discussion on cross-linguistic vowel perception. Subsequent chapters on fricatives (Chapter 7), stops and affricates (Chapter 8), and nasals and laterals (Chapter 9) follow a similar format of presentation: the acoustic properties, auditory representations, and perception of the sounds.
Overall, this is an excellent introduction to the acoustics of speech. In many ways it reminds me of the text by Ladefoged (1996): they are both compact in size but manage to cover major topics in acoustic phonetics with a unified theme in an approachable manner. For Johnson (2003), the overarching theme is to relate the acoustics of speech to predictions from the acoustic theory of speech production. The presentation of the acoustic theory is distributed nicely in relevant chapters (e.g. voicing source and tubes in the chapter on vowels, noise source in fricatives, and bandwidth in nasals) such that each chapter is kept concise without sacrificing the depth of discussion. The author does an admirable job in introducing the physical basis of speech and acoustic modeling in a non-technical way, which is particularly helpful for readers who may not have much mathematical background. The analogies drawn to illustrate key concepts give the book a user- friendly feel. I also like the "semi-related stuff in boxes", explaining in simple terms the concepts that many of us have always wanted to know but never really understood well from more technical references.
The emphasis on the role of the auditory and perceptual system is another attraction of the book. As the author notes, "the auditory system warps the speech signal in some very interesting ways, and if we want to understand the linguistic significance (or lack of it) of speech acoustics, we must pay attention to the auditory system." In the chapters on major classes of sounds, comparisons are made between auditory and acoustic representations of speech to alert readers of the importance of the auditory/perceptual system. Similarly, the role of linguistic experience in shaping how speech sounds are perceived is also highlighted with data from cross-linguistic speech perception.
In addition to be used as a supplement to a general phonetics or speech science text as the author suggests, this book makes a good companion for a laboratory course in acoustic phonetics. In particular, the chapter on digital signal processing gives detailed explanations of how various speech analysis techniques are derived. This information is particularly useful in how to choose the appropriate analysis and how to interpret the acoustic data for the research question. In addition, the chapter on speech perception is a welcome addition to this new edition. Consistent with the theme that attention should be paid to the auditory and perceptual side of phonetics, it illustrates how a perception experiment is designed and how the results are interpreted.
Since this book is intended as an introductory text, the scope and depth of coverage is inevitably compromised in exchange for brevity and readability. It might be helpful to provide a list of suggested readings for readers wishing to further explore the topics, like what Pickett (1999) did for example. Furthermore, although this book is aimed to discuss the acoustic and auditory aspects of phonetics, more discussion on the articulation of speech seems warranted given that speech acoustics is mainly a product of speech articulation. It will complement the theme in relating speech acoustics to modeling from the acoustic theory of speech production, which is what makes this book unique.
In sum, if you want to know about the articulatory-acoustic-phonetic relationships but find Stevens (1998) a little overwhelming, I highly recommend reading this book first.
Ladefoged, P. (1996). Elements of Acoustic Phonetics. The University of Chicago Press.
Pickett, J. M. (1999). The Acoustics of Speech Communication. Allyn and Bacon.
Stevens, K. N. (1998). Acoustic Phonetics. MIT Press.
ABOUT THE REVIEWER:
ABOUT THE REVIEWER Chao-Yang Lee received his graduate training in the cognitive and linguistic sciences from Brown University. His research interests include the role of lexical tone in spoken word recognition and the nature of phonetic categories. He is currently a postdoctoral associate at MIT and will join the School of Hearing, Speech and Language Sciences at Ohio University in fall 2003.