The significant variability in speech recognition abilities for listeners with at least a mild sensorineural hearing loss (SNHL) cannot be fully explained by reduced audibility. Thus, many have focused on suprathreshold tasks such as frequency and temporal resolution. There are two major confounds, however, that may be present in such studies. First, the hearing-impaired listeners are often elderly. This is important because there is evidence of age-related changes in speech recognition, frequency selectivity, and temporal resolution. Second, permanent hearing loss may affect multiple sites in the auditory system to varying degrees for different patients, contributing to the wide range of variability often seen and making it difficult to determine the effects of one particular structure on auditory perception. Most hearing loss affects at least the outer hair cells (OHCs). Thus it is especially important to understand the effects of OHC damage on auditory perception. Quinine will cause a temporary hearing loss due to its action on the OHCs, and can be used to answer two primary research questions. First, what are the effects of hearing loss due to OHC damage on speech recognition, and in particular on the relationship between speech recognition and suprathreshold processing measures of frequency selectivity and temporal resolution? Second, what are the effects of OHC damage on cochlear compression? Previous results are mixed as to whether hearing loss reduces the magnitude of compression or simply reduces the range of levels over which compression is observed. By estimating compression in listeners with a quinine-induced hearing loss, it will be possible to use a within-subjects design to note changes in the properties of compression. Relevance: There are approximately 28 million individuals in the United States who experience hearing loss. As such, it is important to gain a better understanding of hearing loss and the perceptual limitations it places on those who suffer from it. The results from this study, which will isolate the effects of a certain structure within the auditory system on perception, may aid in the refinement of rehabilitative devices for hearing- impaired listeners.
