Across-Frequency Delays Based on the Cochlear Traveling Wave: Enhanced Speech Presentation for Cochlear Implants

Cochlear implants stimulate the auditory nerve with the outputs of a bank of narrow-band filters. We propose that cochlear implant users are better able to perceive speech when these frequency bands are desynchronized, as occurs in the normal cochlea. The first part of this study was a computational investigation of across-frequency delays on the stimulation patterns generated by the advanced combination encoder (ACE) sound-processing strategy. By offsetting frequency bands from each other, fewer stimuli were discarded from voiced speech by maxima selection. Background noise, however, was not affected in this way. The second part of this study was an assessment of speech perception with across-frequency delays in cochlear implant users with the ACE strategy. In the perception of sentences in noise, three subjects improved with delays, four showed no change and one was worse. For words in quiet, four subjects had improved word recognition and four showed no change. A significant group improvement (P<0.05) was seen for speech in quiet. These results are encouraging for cochlear implant sound processing because across-frequency delays can be incorporated easily and efficiently into existing sound-processing strategies.