Many people with hearing loss (HL) who could benefit from hearing aids (HA) choose not to use them because of limited benefit and poor sound quality. Current HA signal-processing strategies improve audibility and attempt to restore cochlear compression, which is reduced or absent when HL occurs. However, other cochlear processes, such as suppression, are also diminished with HL, but have received less attention. Normal cochlear suppression, the reduction in the response to one sound by the simultaneous presentation of another sound, is important in the processing of complex stimuli, such as speech. The long-term goal of this research program is to restore cochlear processes that are diminished when HL occurs by developing innovative signal-processing strategies. We plan to base the signal-processing design on knowledge of fundamental cochlear processes. The goal of this proposal is to improve HA benefit and increase satisfaction for persons with HL by coupling individualized fitting procedures based on loudness data with processing strategies that restore suppression. Loudness data may offer better prediction of HA benefit because, unlike thresholds, it quantifies HL across a range of sound levels. The goal of this proposal is to integrate the restoration of cochlear suppression and normal loudness into HA signal processing to improve speech perception and user satisfaction, ultimately promoting HA use. A signal-processing algorithm (referred to as the suppression hearing aid, SHA) has been developed and preliminary data have been encouraging. However, further testing and additional data are needed to determine the extent of the benefits. Hypotheses will be tested by pursuing two specific aims: (1) Determine the efficacy of restoring normal loudness growth for broadband sounds, and (2) Evaluate the performance of SHA in non-stationary masking noise.
In Aim 1, the hypothesis that combining gain prescription that restores normal loudness for tones with signal processing that restores suppression will be effective in restoring normal loudness for broadband sounds will be tested. Data gathered under this aim will inform our understanding of the role of suppression in loudness summation. The instantaneous compression of SHA preserves temporal speech cues without deleterious effects on speech quality, while suppression preserves spectral cues.
Aim 2 tests the hypothesis that listeners with HL, who have difficulties processing speech in noisy environments, will benefit from the preservation of speech cues provided by SHA processing and obtain speech-perception benefits in the presence of non-stationary noise. We hypothesize that SHA will provide access to speech cues during spectral and temporal dips in the noise, enabling listeners with HL to "glimpse" speech during the dips. The proposed research will inform our understanding of cochlear processes when HL is present in ways that may lead to other sophisticated processing strategies that go beyond providing amplification and compression.
The purpose of this research program is to provide scientific support for the need to base the design of signal-processing strategies for hearing prostheses on knowledge of fundamental cochlear processes and to develop innovative signal-processing strategies to restore the cochlear processes that are diminished when hearing loss occurs. Restoring cochlear processes that are diminished when hearing loss occurs can improve speech perception, increase user satisfaction, and promote use of hearing technology, such as hearing aids. The work addresses a significant problem faced with increasingly frequency by the aging population in the United States. Therefore, the proposed research is relevant to the NIH's mission of applying scientific knowledge as a basis to reduce disability and improve health.