The effect of a steep high-frequency hearing loss on growth-of-masking functions in simultaneous masking for fm < fs

In normal-hearing subjects, the slope of the growth-of-masking (GOM) function obtained in simultaneous masking when the masker frequency (fm) is much less than the signal frequency (fs) often changes from a value near 2.0 to a value near 1.0 at high levels. The purpose of the present study was to evaluate whether this change in slope reflects a basal shift in the peak of the signal's basilar-membrane vibration pattern. To discourage the use of basally shifted peak excitation, GOM functions were obtained in seven subjects with a precipitously sloping high-frequency hearing loss. The signal was located at the normal-hearing edge of the loss, and the masker was located 3 equivalent rectangular bandwidths below fs. In addition, GOM functions for an fs of 2000 Hz were obtained in four subjects with normal hearing, either “in quiet” or in the presence of a restrictor tone with a frequency of 2400 or 2600 Hz and a level of 90 dB SPL. Overall, the results generally are not consistent with the change in slope at high levels being due to a basal shift in the peak of the signal's basilar-membrane vibration pattern. Instead, the results are consistent with a decrease in compression at high input levels at the place corresponding to fs.