ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

1pSP12. Stimulus intensity and fundamental frequency effects on duplex perception.

Houri K. Vorperian

Dept. of Commun. Disord., Univ. of Wisconsin--Madison, Madison, WI 53705

Marleen T. Ochs

D. Wesley Grantham

Vanderbilt Univ., Nashville, TN 37232-8700

The simultaneous perception of speech and nonspeech occurs when the intensity of the F3 transition of a three formant synthetic syllable is increased relative to the rest of the syllable (the base). This phenomenon has been interpreted as evidence of a distinct system for speech perception that precedes other specialized systems of general auditory processing [Liberman and Mattingly, Science 243, 489--494 (1990)]. Using F3 transitions with fundamental frequencies different from the base, and referencing their presentation levels to the level at which each F3 transition was barely audible in the context of the base, identification functions were obtained across a wide range of F3 transition intensities. As previously demonstrated, results showed that the F3 transitions contributed to the speech percept over a wide range of intensities and fundamental frequencies. However, at very intense F3 transition levels, /ga/ identification decreased. Also, both /da/ and /ga/ identification progressively decreased as the fundamental frequency of the F3 transition increasingly differed from the base and interacted with intensity. These findings indicate that information from general auditory processing systems is available to the specialized speech perception system. The speech perception system tolerates a range of information from general auditory processing systems before it rejects such information as irrelevant to speech.