Effect of masker duration and masker level on forward and backward masking

Abstract

Temporal masking of clicks by noise was investigated using forward and backward masking paradigms. The level and duration of the noise and temporal separation, Δt, between the click and noise were varied. There are three primary findings. First, for Δt less than 1 msec, as the noise level increased by 20 dB the click threshold increased by 20 dB. Between 1 and 10 msec the increase depended on Δt, so that the signal-to-noise ratio was not preserved. Second, the duration of the masker did not greatly affect the click threshold when Δt was brief (0.1 msec) or long (100 msec). For intermediate Δt's, the threshold increased by as much as 30 dB as the noise duration increased from 1 to 625 msec. Third and finally, for very brief Δt's, under some conditions, detectability actually improved as the click was moved closer to the noise. The theoretical implications of these results are discussed in terms of various theories of temporal integration.