Speech Perception as a Function of the Number of Channels and Channel Interaction in Cochlear Implant Simulation

Abstract

Objective: Speech perception relies on precise spectral and temporal cues. However, cochlear implant (CI) processing is confined to a limited frequency range, affecting the information transmitted to the auditory system. This study analyzes the influence of channel interaction and the number of channels on word recognition scores (WRS) within the CI simulation framework. Methods: Two distinct experiments were conducted. The first experiment (n=29, average age =23 years, 14 females) evaluated the number of channels using eight, twelve, sixteen, and 22 channel vocoded and non-vocoded word lists for WRS assessment. The second experiment (n=29, average age =25 years, 16 females) explored channel interaction across low, middle, and high-interaction conditions. Results: In the first experiment, participants scored 57.93%, 80.97%, 83.59%, 91.03%, and 95.45% under 8, 12, 16, and 22-channel vocoder and non-vocoder conditions, respectively. The number of vocoder channels significantly affected WRS, with significant differences observed in all conditions except between the 12-channel and 16-channels (p<0.01). In the second experiment, the participants scored 2.2%, 20.6%, and 50.6% under high, mid, and low interaction conditions, respectively. Statistically significant differences were observed across all channel interaction conditions (p<0.01). Conclusions: While the number of channels had a notable impact on WRS, it is essential to note that certain conditions (12 vs. 16) did not yield statistically significant differences. The observed differences in WRS were eclipsed by the pronounced effects of channel interaction. Notably, all conditions in the channel interaction experiment exhibited statistically significant differences. These findings underscore the paramount importance of prioritizing channel interaction in signal processing and CI fitting.