The relation between auditory grouping and comodulation masking release.

Abstract

The feature of coherent amplitude modulation across frequency, which gives rise to the phenomenon of comodulation masking release (CMR), is also considered to be a cue for auditory grouping. This commonality raises the question of whether it is a prerequisite for CMR that the correlated noise bands comprising the masker be grouped together. The present study measured signal threshold in the presence of correlated bands of noise under conditions designed to discourage the fusion of the noise bands. In the first set of conditions, the onset/offset synchrony between the noise band centered on the signal and the comodulating flanking bands was manipulated. The results indicated that the CMR measured when the on-signal band and flanking bands were gated synchronously was largely eliminated with onset/offset asynchronies of 50–100 ms (on-signal band beginning before and ending after the flanking bands). In the second set of conditions, signal threshold in the on-signal band was measured in the presence of a single flanking band, either with or without a background harmonic complex that included in its harmonic series the center frequency of the flanking band, but not the on-signal band. No consistent effect of harmonicity was observed. [Work supported by AFOSR.]