Relationship between psychophysical tuning curves and "suppression".

This study examined two-tone unmasking and auditory frequency selectivity about 3 kHz for the purpose of demonstrating a qualitative relationship between the two. An adaptive 2IFC forward-masking procedure was used to collect psychophysical tuning curves (PTC's) and two-tone masking data under a quiet and noise condition for the same normal-hearing listeners. In the noise condition, a narrowband noise masker, centered one decade down from the probe, was gated on with the tonal masker(s). Kiang and Moxon [J. Acoust. Soc. Am. 55, 620-630 (1974)] have found that low-frequency narrowband noise serves to decrease the sharpness of electrophysiological tuning curves by affecting only the tip segments. The data for four highly practiced listeners indicate that the gated-noise masker was effective in broadening the PTC's and in lessening the magnitude of two-tone unmasking. The mutually reflected changes in tuning curves and in two-tone unmasking indicate a close relationship between frequency selectivity and unmasking: the greater the magnitude of unmasking above the center frequency of the PTC, the sharper the tuning of the PTC.