A comparison of psychophysical tuning curves in simultaneous and forward masking

Abstract

Threshold for a short‐duration pure‐tone signal depends upon the signal's temporal position within a longer duration pure‐tone masker, particularly for masker frequencies above the signal frequency [Bacon and Viemeister, J. Acoust. Soc. Am. Suppl. 1 76, S75–76 (1984)]. We have extended the previous work to show how this temporal effect influences a common measure of frequency selectivity. Psychophysical tuning curves (PTCs) were measured for a 20‐ms, 1‐kHz signal presented at 10‐dB sensation level and positioned at the beginning, at the center, at the end, or immediately following a 400‐ms masker. In simultaneous masking, the PTCs were broadest for the signal at masker onset, and sharpest for the signal at the center; the differences were largest on the high‐frequency side. For two of the three subjects, the forward masking PTC was sharper than any of the simultaneous masking PTCs. For one subject, however, there was little difference between the forward and the simultaneous masking PTC with the signal temporally centered. These results indicate that, at least for short‐duration signals, the frequency selectivity measured with simultaneous masking PTCs, and the degree of sharpening revealed in forward masking PTCs, depend upon the temporal position of the signal within the simultaneous masker. [Work supported by NIH and MRC.]