Perceptual effect of reverberation on multi-microphone noise reduction for cochlear implants

The combination of noise and reverberation make listening conditions difficult for cochlear implant (CI) users. The perceptual effect of reverberation was evaluated via speech intelligibility tests with CI users. A fixed directional microphone, an adaptive directional microphone and a beamformer post-filter were evaluated. Reverberation was varied by changing the target and noise distance and by simulating a highly reverberant room with concrete surfaces. CI performance expectedly degraded as the target distance was increased, but the benefit of noise reduction was unaffected by listening distance. In the highly reverberant condition, CI performance was severely degraded, but noise reduction benefit remarkably increased, especially for the beamformer post-filter algorithm. All directional processing algorithms were suitable for use in noisy reverberant conditions and the best outcome was provided by the post-filter condition.