Effects of speaking rate on voice-onset time and vowel production: Some implications for perception studies

Abstract

An examination of studies investigating effects of speaking rate on speech production and speech perception reveals an apparent conflict between acoustic data from speech production and the acoustic parameters typically manipulated in speech perception experiments. This note is intended to address the apparent conflict in the literature by examining both production and perception studies in the extant literature, and by analyzing new data on the effects of speaking rate on voice-onset time (VOT) production in English. Subjects were asked to read CVC words in context at both slow and fast rates of speech, and the relationship between VOT and vowel duration across changes in speaking rate was then examined. The data for voiceless stop plus sound sequences indicate that as speaking rate slows both VOT and vowel duration increase in almost equal proportions. Importantly, there is no evidence that VOT and vowel length vary inversely such that as VOT increases, vowel length decreases. In contrast, most perception experiments examining the effects of speaking rate on VOT use stimulus parameters that do vary inversely VOT and vowel length. Thus, the perceptual the effects obtained under such conditions may not be appropriately attributable to perceptual effects of speaking rate on phonetic categorization, but rather may be due to other perceptual effects.