Speech rate influences on the perception of stop voicing

Abstract

Measures from speakers of British English show that voice-onset times (VOT's) produced in prestressed, prevocalic stop-consonants decrease as speech rate increases. Complementary adjustments occur in perception: if the syllabic rate of a synthetic precursor phrase which introduces test syllables drawn from a CV VOT continuum is increased, phoneme boundaries shift to shorter VOT's. The perceptual effect (a) is dependent upon timing variations in at most the 750 msec of the precursor immediately preceding the test syllable; (b) is almost unaffected by a mismatch of vocal tract length between precursor and test syllable; and (c) is substantially diminished if the silent closure interval between precursor and test syllable is longer than about 100 msec. These results suggest that the effect is not subsumed by the perceptual extraction and application of a speaker-dependent, speech-rate parameter but depends upon immediate computations of timing relations over short stretches of perceptually continuous running speech. Further experimentation is required to specify how perceptual measures of the durations of the vowels, the closure interval and the VOT, in VCV contexts, interact and so to determine the status of these variables as cues and/or contexts for the perception of stop voicing in running speech. [Work supported by J.S.R.U. at The Queen's University of Belfast, U.K.]