Effect of vowel duration on the perception of syllable-initial /∫/ and /t∫/

The duration of an adjacent vowel has been demonstrated to affect the judgment of consonant duration and, hence, phonetic identity. For example, syllable-initial stops can be distinguished from glides on the basis of transition duration and, when the following vowel is relatively long, longer transitions are required in order for a glide to be perceived. Apparently, the vowel provides a source of durational contrast, whereby a longer vowel makes the adjacent consonant seem shorter. This effect has been demonstrated for both speech and nonspeech signals [L. Diehl and M. A. Walsh, J. Acoust. Soc. Am. Suppl. 1 80, S125 (1986)], and is presumably grounded in a general auditory mechanism. In this study, the effect of vowel duration on perception of syllable-initial consonants is also demonstrated for fricatives and affricates. Frication duration is an important cue to this distinction, with longer durations yielding more /∫/ responses. Two series of edited natural tokens of /∫a/ and /t∫a/ were created in which frication duration varied from 100 to 210 ms. The duration of the following vowel was 204 ms for one series, and 358 ms for the other. With the longer vowel context, significantly longer frication was required to yield a /∫/ percept. Consistent with earlier findings for other consonantal distinctions, durational contrast occurred between the vowel and fricative. [Work supported by NINCDS.]