Maximizing speech recognition under adverse listening conditions

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Project Summary/Abstract Currently, little is understood about the interactions of temporal processing abilities, hearing loss, and amplification or how these factors impair transmission of the speech temporal envelope and exacerbate temporal masking. This proposal targets this knowledge gap by defining the acoustic and perceptual cues that determine how older adults with normal and impaired hearing with and without amplification use the temporal envelope for speech recognition in challenging conditions. Effects of age and hearing loss will be assessed by defining suprathreshold contributions from temporal processing and cognitive abilities. The central aim is to examine and identify the most informative auditory cues when only partial speech information is available in noisy environments for older listeners when audibility is restored. The central hypothesis is that communication abilities in realistic listening environments can be maintained or improved by preserving temporal envelope properties of specific speech events and by reducing modulation masking. Aim 1 will determine the acoustic and perceptual contribution of temporal envelope cues within specific speech events. Five different listener groups enable the investigation of age, cochlear pathology, and amplification contributions to speech recognition based on specific temporal properties of the speech envelope. These properties will be isolated using combined temporal filtering and amplitude compression methods. Aim 2 will assess the acoustic and perceptual consequences of speech modulation masking imposed by the temporal envelope of a single competing talker. Extended glimpsing models will acoustically define preserved amplitude and frequency modulations during modulation masking for natural and vocoded (i.e., envelope-only) sentences. Aim 3 will determine the acoustic and perceptual consequences related to the temporal effects of spectral shaping, which represents the minimum processing of hearing aids used to ensure audibility, for varying degrees of hearing loss severity. The long-term goal of this project is to define acoustic parameters for enhanced hearing aid programming in modulated noise, such as a competing talker, and identify individual processing abilities to assist in future customization of these devices and auditory training protocols. The significant contribution of this project is in defining the key acoustic properties of the speech temporal envelope that must be preserved to maximize speech recognition in temporally complex noise by older adults with hearing loss and concomitant suprathreshold temporal processing deficits. This project implements an innovative theoretical framework to guide acoustic analyses and define the perceptual processing of speech temporal envelope modulation in the presence of a temporally complex competing signal. These innovations allow for the direct investigation of the effects of amplification on speech modulation masking for individual temporal properties of the speech signal due to a single competing talker, quite arguably the most difficult listening condition for older listeners.