On the growth of masking asymmetry with stimulus intensity

Abstract

Masking asymmetry was investigated over a wide range of stimulus intensities for two signal frequencies, f 0=1.0 and 4.0 kHz, using both fixed‐masker and fixed‐signal paradigms. The masker was a notched noise with the upper and lower edges of the notch, f u and f l , respectively, placed asymmetrically about f 0. For various notch widths, the asymmetry of masking was measured as the difference between the masked threshold obtained when f l was nearer f 0 and that obtained when f u was nearer f 0. For maskers with wide notches, (f u −f l )/f 0>0.15, masking asymmetry changed with stimulus level; at the highest level, masked threshold was greatest when f l was nearer f 0, and, at the lowest level the asymmetry reversed slightly for f 0=1.0 kHz so that masked threshold was actually greater when f u was nearer f 0. Nonparallel growth of masking functions reveal changes in masking asymmetry with signal level as well as with masker level. It is concluded that the nolinear growth of masking with level is due primarily to changes in the auditory filter, rather than changes in the detector following the filter.