Physiological and Acoustic Studies of Speech\n

Physiological and Acoustic Studies of Speech
We are studying the relation between three levels in the speech chain: the discrete phonological representation of an utterance, the acoustic pattern that results from the utterance, and the articulatory gestures that create the link between the phonological and acoustic representations. One area of research is Quantal Theory, which states that the distinctive features or contrasts that form the basis of the phonological representation appear to be grounded, at least in part, in the physics of human sound production and on properties of the response of the auditory system to these sounds. Current projects focus on the role of the compliant vocal-tract walls in shaping the sound pattern for obstruent consonants, the nature of the rapid spectrum change at the release of a nasal consonant, and the role of the subglottal system in defining some basic place distinctions for vowels and vowel-like sounds. A second area of research is the variability that occurs in the process of formulating an array of articulatory gestures from the phonological representation of an utterance. This variability arises in part from the introduction of context-dependent enhancement gestures and from the overlap of gestures from adjacent segments. Based on acoustic analysis, we attempt to formulate principles that govern or constrain enhancement gestures and gestural overlap. A third area of research is developmental speech. In the early years of life, a child is exposed to the variable acoustic pattern of speech and to her own vocalizations, and from this and other experience with the environment must uncover the units of the phonological representation of language. Through acoustic analysis of utterances produced by children in the age range 3-7 years we attempt to provide a quantitative description and interpretation of this development based on a set of acoustic measures that describe a child’s emerging ability to produce patterns of gestures for vowels, consonants, and prosodic units that are derived from a phonological representation.