Acoustic Phonetics – Stevens

A second observation is that, as long as the articulatory gestures associated with the various features of a segment are implemented, there are usually acoustic consequences of these gestures that permit the features to be recovered from the sound. These acoustic con- sequences and their representation in the peripheral auditory system can be predided from articulatcry-acoustic-auditory relations of the type described in chapters 1 through 4.

Finally, although it can be argued that words are stored in memory in terms of segments and features, a speaker may modify some of these features in casual speech. However, .there are strong con- straints on the types of feature modifications that are allowed. A listener must resort to knowledge of the language at levels above the segment and feature to recover the words from such casually produced utterances.

Some In8uences of Contexton Speech Sound Production Notes Chapter 1 1. The acousticrelevanceof thisparameterderives from the expressionfor the acousticmassof ,a short tube,MA = pt/A, where p =density of air, I =length of tube,andA =aoss-sedional area of tube. 2. The meaningof modal ooicing is discussed in more detail in section 2.1.

3. The estimationsof the glottal opening for voiced and voiceless fricative consonantsare based on several kinds of indirect evidence.Simultaneous records of subglottal pressure and intraoral pressure during fricativeconsonant production (Ladefoged. 1963) show that the intraoral pres- sure is slightly less than the subglottal pressure. indicating a small pressure drop at the glottal constriction.

Furthennore, the more extensive data on intraoral pressure in the absence of sub- glottal pressure records (Hixon,1966; Arkebaueret al.• 1967) always indicate that the intraoral pressureis somewhat below the subglottal pressurethat is nonnally used in speech. 4. It has been observed by Peter Ladefoged (personalcommunication, 1997) that in a language such as Pirahi. a sequenceof three consecutivevowels can have alternating tones in which the time between high tone peaks is usually about 150 ms (e.g., the word lbaaati, to make a path).

suggesting that the minimum times given above could be reviseddownward. Chapter 2 1. The effectivemechanical compliance of the lower mass when the upper mass forms a com- plete closureis given by Ci = CtC,/(Ct + C,). where Ct and C, are the mechanical compliance of the lower massand the couplingcompliance between the two masses. respectively. as shown in figure2.2. 2. Thefactor of 2 takes into accountthe contribution of positive and negative frequencies. Chapter 3 1. When the cross-sectional areachanges abruptly over some portion of thelength of the vocal tract, the wavefronts can deviate from plane waves.

The application of quantitative modeling methods to the acoustics of speech sound production underwent a major advance with the work of Gunnar Fant. His book, Acoustic Theory of Speech Production, together with his continuing work and that of his students and colleagues in the 1960s, 1970s, and 198Os, has been a major stimulus to raising the field of acoustic phonetics toward the level of a quantitative science.This book attempts to build on this earlier work of Fant and others over these decades.

The aim of the book is to present a theory of speech sound generation in the hwnan vocal system. The acoustic aspects of this theory are grounded in a representation of speech sound production as the creation of sound sources in the vocal tract and the filtering of these sources by the vocal tract airways. The sources can be of various kinds, including the quasi-periodic laryngeal source, noise due to turbulent airflow, and transient sounds. Since the articu- lators move with time, the sound sources and the filtering also change with time.

Examination of the time-varying sources and filtering leads to the observation that some aspects of the transformation from articulation to sound are categorial. That is, the types of sound sources and the filtering of these sources can be organized into classes. These classes are closely related to the discrete linguistic categories or features that describe how words appear to be stored in the memory of a speaker or listener.

The theme of this book is to explore these relations between the discrete linguistic features and their articulatory and acoustic manifestations. The book begins with a review of the anatomy of the speech production system, and a discussion of some principles relating airflows and pressures in the vocal tract.

The next four chapters describe mechanisms of sound source generation in the vocal tract, present theories of the vocal tract as an acous- tic resonator excited by these sources, review some principles of auditory psychophysics and auditory physiology as they may be relevant to auditory processing of speech, and present an introduction to phonological repre- sentations.

With these five chapters as background, the remaining chapters are devoted to a detailed examination of the vowels (chapter 6), the con- sonants (chapters 7 to 9), and some examples of how speech sounds are influencedby context (chapter 10). Uttle attention is given to the description and modeling of the production of sounds in languages other than English. The aim is not to be complete, even for the sounds of English, but rather to present an approach to model- ing the production of speech sounds in general.

This is a short excerpt from the opening of “” by Unknown, quoted for review and introduction purposes. All rights belong to the copyright holders.

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