Using binaural beat sensitivity to explore mechanisms of bimodal temporal envelope beat sensitivity

Abstract

Current cochlear implant (CI) fitting strategies aim to maximize speech perception through the CI by allocating all spectral information across the electrode array without regard to tonotopic placement of each electrode along the basilar membrane. For patients with considerable residual hearing in the non-implanted ear, this approach may not be optimal for binaural hearing. This study aims to explore fitting procedures in which CI maps better complement information from the acoustic ear by reducing the frequency mismatch between them. We investigate the mechanisms of binaural temporal-envelope beat sensitivity in normal-hearing listeners using bandpass filtered pulse trains with parameters including stimulus level, filter bandwidth, filter slope, and spectral overlap using bandpass filtered pulse trains. We find the minimum baseline interaural timing difference and spectral mismatch that normal-hearing listeners can tolerate while maintaining their ability to detect interaural timing differences. Initial results consistently demonstrate maximum sensitivity to binaural beats when place of stimulation is matched across ears. The outcomes of this study will provide new information on binaural interactions in normal-hearing listeners and guide methodology for incoming single-sided-deafness patients as we adjust their CI maps in an effort to reduce the frequency-mismatch. [Work supported by NIH grant F32DC016815-01.]