Modeling the effects of peripheral nonlinearity in listeners with normal and impaired hearing

Recent physiological studies of basilar rnembrane (BM) mechanics indicate that the response to tones presented at the characteristic frequency (CF) is nonlinear and cornpressive. Input-output functions show marked compression at medium input levels and become more linear at very low and very high levels. Damage to the cochlea, in particular the outer hair celis, generally results in a loss of sensitivity and a linearization of the BM transfer function. In this study we assume that listeners with cochlear hearing loss also exhibit reduced BM compression, and we investigate some possible psychoacoustic consequences of the reduced nonlinearity. Results from nonsimultaneous rnasking experiments in norrnally hearing listeners were modeled using a temporal window model, preceded by a compressive nonlinearity (Oxenham & Moore, 1994). When modeling sirnilar data from hearing-impaired listeners, only the input nonlinearity of the model was changed. The results suggest that the change in nonlinearity may be sufficient to account for some differences in performance in the additivity of nonsimultaneous masking, the decay of forward masking with increasing masker-signal interval, and the growth of forward masking with increasing masker level.