Impact of cochlear implant processing on acoustic cues critical for room adaptation

Typical-hearing listeners are generally resilient to distortions in low to moderate reverberant environments, whereas cochlear implant (CI) users are significantly affected. Typical-hearing listeners adapt to a reflective space through short-term learning from prior exposure to the distortion patterns, which enhances signal comprehension. This adaptation relies on specific acoustic cues, such as attenuation of modulation depth in the temporal envelope, spectral coloration introduced by the room, and statistical properties of the reverberation tail, including skewness and kurtosis. It remains unclear how CI processing alters these acoustic cues and whether they are accessible to CI users. To investigate, dry and reverberant speech signals were analyzed before and after simulating key stages of CI signal processing, including dynamic range compression, bandpass filtering, envelope extraction, and current spread. Preliminary findings suggest CI processing causes slightly greater attenuation of the speech envelope’s modulation depth compared to reverberation alone relative to the dry signal. Additionally, room-induced spectral coloration was altered by CI processing, and reductions in the kurtosis and skewness of the reverberation tail were observed. These findings may partially explain why CI users struggle in reverberant environments.