Modeling hearing loss an an additional sources of masking

When presented with a masker at a fixed sound pressure level, Listeners with sensorineural hearing loss often have elevated masked thresholds compared to listeners with normal hearing. It is possible to account for this effect by assuming that the hearing loss itself reflects an additional source of masking that combines with the effect of a single external masker in the same nonlinear way that the effects of two external maskers combine. This hypothesis, previously evaluated by Humes, Espinoza-Varas, and Watson (1988), is reconsidered here using several additional sets of data, including data from Leek and Summers (1993), for multiple simultaneous maskers. The difference between masked thresholds in normal-hearing and hearing-impaired listeners varies as a function of the magnitude of the masking effects relative to both normal quiet threshold and the degree of hearing loss. Power-law models of additivity of masking provide a simple description of these complex relationships and a useful framework for development of more detailed models.