Individual Differences with WDRC Amplification in Challenging Environments

Northwestern University, Evanston IL

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Abstract

Summary There are an estimated 31 million Americans with untreatable hearing loss who experience an impaired ability to communicate in complex listening environments (i.e., those including noise and reverberation). While hearing aids are the most commonly prescribed means of hearing treatment, hearing aid users are frequently dissatisfied with their hearing aid's performance in complex listening environments. Studies have indicated that communication in these environments can be improved with noise-suppression hearing aid processing recommendations: digital noise reduction (DNR) and cognition-based wide-dynamic range compression (WDRC) speed. However, these studies have not accounted for the fact that real listening environments inevitably include some amount of reverberation. Reverberation additionally adversely affects speech perception and distorts many of the acoustic cues to which DNR and WDRC are sensitive. The inevitable presence of reverberation in the real world may decrease the efficacy of noise-suppression hearing aid processing recommendations. Thus, reverberation might account for the discrepancy between laboratory benefit and real-world benefit. The results of the proposed project may provide clinicians with more realistic expectations of the benefit that can be expected from these noise- suppression recommendations, and also provide a knowledge base for development of improved hearing aid algorithms. The project will consist of two experiments: (1) evaluating the benefits of DNR under reverberant conditions and (2) evaluating the benefits of cognition-based WDRC speed under reverberant conditions. Older individuals with mild-to-moderate sensorineural hearing loss will be tested in both experiments. Listeners will undergo a cognitive test battery to assess cognitive function. A set of low context sentence stimuli will be processed in several stages: (1) sentences will be combined with two-talker modulated ICRA noise at several signal-to-noise ratios; (2) speech-in-noise stimuli will be processed with a reverberation simulator at several reverberation times; (3) reverberated speech-in-noise stimuli will be processed with either DNR hearing aid simulation (experiment 1) or WDRC hearing aid simulation (experiment 2). A novel acoustic analysis method will be used to quantify the signal-to-noise ratio changes as a result of hearing aid processing across reverberant conditions. Additionally, behavioral measures will include listener intelligibility (sentence recall), sound quality (pair-wise comparisons), and listening effort (dual-task paradigm). Data for both experiments and for each outcome measure will be analyzed using 3-way ANOVAs with signal- to-noise ratio, hearing aid processing (DNR vs. no DNR [experiment 1] or fast-acting WDRC vs. slow-acting WDRC [experiment 2]), and reverberation time as within-subject variables. Overall, the goal of the proposed experiments is to quantify the amount of benefit of hearing aid noise-suppression algorithms across a range of reverberation times indicative of real-world listening.