Interaural spectral mismatch and binaural fusion in simulated cochlear-implant listening for single sided deafness

Abstract

Cochlear implants (CIs) can restore some spatial-hearing capabilities for individuals with single-sided deafness (SSD). However, there is a considerable variability in outcomes among SSD-CI listeners. One possible cause is spectral mismatch between the acoustic and CI ears. Vocoder simulations of SSD-CI listening were used to investigate the effect of interaural spectral mismatch on subjective fusion for normal-hearing listeners. A virtual cocktail party was created by presenting combinations of 1-6 concurrent talkers to the left, right or both ears. After each trial, listeners were asked how many total voices were heard. If listeners were able to perceptually fuse the voices that were presented to both ears, they should be more likely to report the correct number of total talkers in the scene. If not, they should report more total talkers. Preliminary results show that listeners reported more total talkers when the vocoded speech was processed with a frequency-matched map (simulating a standard CI frequency allocation) then with a place-matched map. These data suggest that place-matched CI mapping has the potential to provide SSD-CI listeners with more opportunities for binaural fusion and improved spatial hearing. This method could be applied to SSD-CI listeners to evaluate mapping strategies and outcomes after implantation. [The opinions and assertions presented are the private views of the authors and are not to be construed as official or as necessarily reflecting the views of the Department of Defense.]