The effect of rate of amplitude comodulation on sentence perception.

Abstract

Previous studies of the perception of time-varying sinusoidal (TVS) sentences suggested that amplitude comodulation may serve as a grouping cue in speech perception [T. D. Carrell, J. Acoust. Soc. Am. Suppl. 1 86, S102 (1989)]. The purpose of the present investigation was to further explore that idea and to evaluate whether the effects observed in TVS studies are related to other temporally based phenomena such as comodulation masking release (CMR). If a common process underlies the perception of amplitude-modulated speech and nonspeech stimuli, then grouping effects should occur in speech perception in a manner similar to that observed in nonspeech studies when the amplitude modulation characteristics are similar. Examined in the present study was the effect of amplitude modulation rate on intelligibility of TVS sentences as compared with rate effects in CMR phenomena. Amplitude modulation rates were 5, 10, 20, 50, 100, and 200 Hz. Although the results suggested that comodulation is important in speech perception, effective rates may be different from those observed in nonspeech tasks. These findings are important for our understanding of auditory object formation of both speech and nonspeech stimuli.