Cochlear-implant simulations of speech in complex acoustic backgrounds

Abstract

Cochlear-implant simulations have shown that good speech intelligibility in quiet can be obtained with very poor spectral resolution and no temporal fine-structure information. It is not known how robust speech is to such processing in the presence of complex interfering sounds. This study examined speech reception for sentences in the presence of four types of interference (broadband noise, broadband noise modulated with a speech envelope, a single male talker, and a single female talker) and three processing schemes (24- and 8-channel cochlear-implant simulations and unprocessed). The spectral resolution in the 24-channel condition was designed to be comparable to that of normal hearing, but the original temporal fine structure was replaced by noise in both the 24- and 8-channel processing conditions. Performance with 24-channel processing was substantially poorer than in unprocessed conditions, despite the relatively good frequency resolution. Eight-channel processing produced the poorest performance. Stimulus processing was generally more detrimental to speech reception in the fluctuating interferers than in the unmodulated noise. The detrimental effects of eliminating fine-structure information may be due to the reduction in pitch cues, which listeners may use to help segregate the sources. [Work supported by NIDCD Grant R01DC05216.]