Judgment of perceptual synchrony between two pulses and verification of its relation to cochlear delay by an auditory model1

Abstract

This study investigates whether the delay caused in the course of wave propagation along the basilar membrane (BM) of the cochlea (i.e., the cochlear delay) affects the perceptual judgment of the synchronization of two sounds. An experiment was conducted to examine the detection of asynchrony using two types of chirps (compensatory and enhanced chirps) and a pulse. A compensatory delay chirp was designed to align the peaks of the BM velocity. An enhanced delay chirp had a delay pattern that "enhances" the assumed cochlear delay. The pulse had a cosine phase relation and, as a result, an intrinsic cochlear delay at the auditory peripheral. The results suggest that it was difficult for the auditory system to distinguish sounds when the lower-frequency components arrived after the higher-frequency components, as happens with a pulse. An auditory model could closely simulate the BM velocity for all stimuli. From both experimental and simulation results, we concluded that the BM velocity corresponding to the higher-frequency components was one of the cues used in the perceptual judgment of synchronization. © 2008 Japanese Psychological Association.