Reduced Channel Interaction Improves Timbre Recognition Under Vocoder Simulation of Cochlear Implant Processing

Abstract

Objective This study aimed to investigate the influence of the number of channels and channel interaction on timbre perception in cochlear implant (CI) processing. By utilizing vocoder simulations of CI processing, the effects of different numbers of channels and channel interaction were examined to assess their impact on timbre perception, an essential aspect of music and auditory performance. Study Design, Setting, and Patients Fourteen CI recipients, with at least 1 year of CI device use, and two groups (N = 16 and N = 19) of normal hearing (NH) participants completed a timbre recognition (TR) task. NH participants were divided into two groups, with each group being tested on different aspects of the study. The first group underwent testing with varying numbers of channels (8, 12, 16, and 20) to determine an ideal number that closely reflected the TR performance of CI recipients. Subsequently, the second group of NH participants participated in the assessment of channel interaction, utilizing the identified ideal number of 20 channels, with three conditions: low interaction (54 dB/octave), medium interaction (24 dB/octave), and high interaction (12 dB/octave). Statistical analyses, including repeated-measures analysis of variance and pairwise comparisons, were conducted to examine the effects. Results The number of channels did not demonstrate a statistically significant effect on TR in NH participants (p > 0.05). However, it was observed that the condition with 20 channels closely resembled the TR performance of CI recipients. In contrast, channel interaction exhibited a significant effect (p < 0.001) on TR. Both the low interaction (54 dB/octave) and high interaction (12 dB/octave) conditions differed significantly from the actual CI recipients' performance. Conclusion Timbre perception, a complex ability reliant on highly detailed spectral resolution, was not significantly influenced by the number of channels. However, channel interaction emerged as a significant factor affecting timbre perception. The differences observed under different channel interaction conditions suggest potential mechanisms, including reduced spectro-temporal resolution and degraded spectral cues. These findings highlight the importance of considering channel interaction and optimizing CI processing strategies to enhance music perception and overall auditory performance for CI recipients.