Effects of masker component phase on the forward masking produced by complex tones in normally hearing and hearing-impaired subjects

The effects of hearing loss on growth-of-masking functions for sinusoidal and complex-tone maskers with differing phase spectra

“…To see whether there was any such effect, three different values of the offset point were used for each masker level and signal frequency; the masker offset ramp started 0, 3.33 or 6.67 ms after the peak in the cosine-phase waveform. Previous results (Carlyon and Datta, 1997;Gockel et al, 2003;Moore et al, 2004b) have shown at most a small effect of the offset point. Given this, our intention was to treat the results for the three offset points essentially as replications.…”

“…There were five listeners in each group. The data for the complex-tone maskers for one normally hearing listener (N1) and one hearing-impaired listener (HI2) were presented in an earlier study (Moore et al, 2004b). The ages of the normally hearing listeners were 59, 21, 52, 21 and 21 years for N1-N5, respectively.…”

“…In the absence of compression and suppression, the slopes of the GOM functions in forward masking should be identical for cosinephase and random-phase complex-tone maskers. Moore et al (2004b) tested this prediction, and found that while phase effects were absent for some hearing-impaired listeners, for other listeners the random-phase masker led to more masking and steeper GOM functions than the cosine-phase masker. Moore et al suggested that, for the listeners showing a phase effect, some cochlear compression might still be present, despite the cochlear hearing loss.…”

“…For these, the slopes of the GOM functions depend on the phase relationship of the components of the complex tone (Alcántara et al, 2003;Gockel et al, 2003;Moore et al, 2004b). The dependence of the slope on the phase spectrum of a complextone masker has been explained in the following way (Carlyon and Datta, 1997).…”

“…Assuming that the amount of forward masking is monotonically related to the RMS or mean value of the compressed waveform evoked by the masker on the basilar membrane, the complex tone leading to the higher peak factor should produce less forward masking, which is generally the case. However, at low sound levels, the basilar membrane response is more linear, so the effect of masker-component phase on forward masking becomes small or zero (Carlyon and Datta, 1997;Gockel et al, 2003;Moore et al, 2004b). The result is that the slopes of GOM functions are steeper for maskers leading to waveforms with a low peak factor on the basilar membrane than for maskers leading to waveforms with a high peak factor.…”