Measuring access to high-modulation-rate envelope speech cues in clinically fitted auditory prostheses

Area of Science:

• Auditory Neuroscience
• Signal Processing
• Speech Perception

Background:

• Hearing impairment affects signal processing, creating trade-offs between audibility and fidelity.
• Reduced access to temporal fine structure (TFS) in hearing impairment necessitates reliance on modulation cues.
• Cochlear implant processing limits TFS transmission, increasing dependence on modulation information.

Purpose of the Study:

• To assess the ability of hearing aid (HA) and cochlear implant (CI) users to access high-rate modulation cues.
• To evaluate the dynamic range of high-rate modulation cue access in these users.
• To compare the performance of clinically fitted hearing aids with simulated high-quality aids.

Main Methods:

• Speech was processed into 8-22 frequency channels, extracting low-rate (EmodL) and high-rate (EmodH) envelope modulations.
• A cross-fading technique combined EmodL and EmodH within channels.
• The processed signal was presented to HA and CI users to assess modulation cue access.

Main Results:

• Clinically fitted hearing aids yielded 10% lower speech intelligibility compared to simulated high-quality aids.
• Cochlear implant users demonstrated an ability to extract high-rate information.
• The dynamic range for accessing high-rate information in cochlear implant users was comparable to that of hearing aid users.

Conclusions:

• Despite signal processing limitations, cochlear implant users can effectively utilize high-rate modulation cues.
• The study highlights the importance of modulation cues for speech intelligibility in hearing-impaired individuals.
• Further research into optimizing signal processing for hearing aids and cochlear implants is warranted.