Synthesis of manner and voicing continua based on speech production models

Abstract

The goal of this project is to create natural-sounding synthetic consonant-vowel syllables for presentation to aphasic patients and normal controls in studies of perception of speech sounds and lexical access. Of particular interest are the manner distinctions that appear to form the basis for the processing of other phonetic dimensions by human listeners. Continua of syllabic-nonsyllabic, sonorant-obstruent, continuant-noncontinuant, and voiced-voiceless sounds were constructed using the KLSYN88 synthesizer. The endpoint stimuli were synthesized based on theoretical models of glottal and turbulence noise sources and vocal-tract filtering, with some refinements to match the characteristics of a particular speaker. Intermediate stimuli were created to form continua that represent incremental changes in the synthesizer parameters. For all stimuli, the values of synthesis parameters modeled utterances that could be produced by a human talker. Identification functions for these continua for normal listeners showed relatively sharp boundaries between phonetic categories. The acoustic characteristics of the stimuli in the vicinity of the boundaries were examined to determine the pattern of acoustic attributes responsible for the abrupt change in identification, such as rise times of amplitudes, rates of change of formants, and relative amplitudes of noise and glottal excitations. [Work supported in part by NIH grants DC00776 and DC00075.]