Signal detection in complex comodulated backgrounds by normal-hearing and cochlear-impaired listeners.

Comodulation masking release (CMR) was investigated in normal-hearing and cochlear-impaired listeners. The narrow-band masker centered on the tonal signal was flanked by a series of other narrow noise bands, some of which had temporal envelopes that were the same as that of the on-signal band (comodulated bands) and some of which had different temporal envelopes (codeviant bands). Previous research using such stimuli with normal-hearing listeners indicated that CMR was often substantially reduced when two codeviant bands were present at spectral locations close to the signal frequency, but that CMR recovered to some extent when more codeviant bands were added. In the present study, cochlear-impaired listeners showed an abnormally large reduction in CMR when codeviant bands were present, and poorer recovery of CMR with increasing number of codeviant bands. Supplementary experiments suggested that the poor recovery of CMR with increasing number of codeviant bands may have been due to the small range (in dB) over which CMR could occur in cochlear-impaired listeners. It is possible that abnormal reduction in CMR with codeviant bands present was due to poor peripheral analysis in hearing-impaired listeners.