The effect on localization of frequency-specific gain reduction schemes when matched and mismatched across ears.

Objective: To evaluate the impact of non-adaptive matched and mismatched gain reduction schemes on localization in spatially-separated noise.

Design: Inspired by the function of commercial noise reduction algorithms, five frequency-specific gain reduction filter schemes were created, three for a modulated babble-noise and two for an unmodulated speech-shaped noise. Applying these schemes as both matched and mismatched conditions across ears, localization of five everyday sounds in noise was measured in a virtual environment using insert earphones. The performance in the reference scheme (no gain reduction in either ear) was measured as well.

Study Sample: Twenty-four adult bilateral hearing-aid users were enrolled in this study.

Results: One of the two mismatched gain reduction schemes for the unmodulated noise had a small but negative impact on localization compared to the reference scheme. For that scheme more high-frequency reduction was noted than for the other schemes. Matching gain reduction across ears restored the deteriorated localization performance. No localization performance differences were observed in the modulated babble-noise regardless of whether the scheme was matched or mismatched across ears.

Conclusions: The impact of noise-induced gain reduction on localization in noise was trivial in the study regardless of whether gain reduction schemes were matched or not across ears.