ASA 124th Meeting New Orleans 1992 October

5aSP2. Perception of voicing in syllable-initial stops at different intensities: Does neural synchrony encode voice-onset?

Keith R. Kluender

Andrew J. Lotto

Rich L. Jenison

Dept. of Psychol., Univ. of Wisconsin, 1202 W. Johnson St., Madison, WI 53706

In response to stop consonants differing in voice onset time (VOT), the dominant synchronization of mid-CF chinchilla auditory nerve fibers changes from the frequencyof F2 to the frequency of F1 at onset of voicing [D. G. Sinex and J. P. McDonald, J. Acoust. Soc. Am. 85, 1995--2004 (1987)]. If this change in neutral synchronization is perceptually relevant for human listeners, changes in stimulus intensity and changes in the frequency difference between F1 and F2 should both affect perception of voicing. In a series of experiments, several continua of synthesized CV's varying in VOT were played to listeners at levels ranging from 40 to 80 dB SPL. The frequency difference between F1 and F2 was manipulated through the use of different places of articulation and different following vowels. Subjects labeled more CV's as voiceless as a function of increasing stimulus level and of deceasing F1--F2 frequency difference. There was also an interaction between stimulus intensity and F1--F2 frequency difference such that the effect of intensity was greater for smaller F1--F2 differences. These effects were reliable across a number of synthetic VOT series, and the effect of intensity extended to a computer edited series of hybrid CV's in which VOT was varied by cross-splicing a naturally produced /da/ and /ta/. The effect of overall stimulus intensity was not affected by amplitude of aspiration energy or by the presence or absence of release bursts. The results provide evidence for synchrony encoding of voicing for stop consonants. [Work supported by NIDCD/NIH Grant No. DC-00719.]