Using a Physical Cochlear Model to Predict Masker Phase Effects in Hearing-Impaired Listeners: A Role of Peripheral Compression

It has been shown that masked thresholds for complex tone maskers may depend on the relative phase between the spectral components of said maskers. Since these masker phase effects are less pronounced in hearing-impaired listeners, it indicates a possible role of peripheral compression. In order to study this phenomenon, we used a previously published physical model of the cochlea. We implemented the model into a version of the temporalwindow model and used it to predict masked thresholds in harmonic complex tone maskers. The predicted thresholds were qualitatively similar with behavioral data (reproduced from the literature) of normal-hearing and hearing-impaired listeners: differences between the maximal and minimal masked thresholds decreased with increasing bandwidth of auditory filters (i.e., with increasing loss of peripheral compression). This effect was independent on the duration of the temporal window. In the predicted data, correlations between the maximum masking difference and the bandwidth of the cochlear filters were significant. However in the behavioral data, the correlations were significant but less pronounced. A loss of peripheral compression affects the isointensity responses of the simulated cochlear filters – broadens the response magnitudes and changes the curvature of the response phases. In the cochlear model, the broadening of the cochlear filters did not compensate for the decrease of the maximum masking difference caused by the changed phase curvature. If the relation between the filter bandwidth and compression loss is the same in the cochlear model and in the real cochlea, the less pronounced correlations observed in the behavioral data may indicate changed temporal resolution or other impairment in the auditory system.