Temporal masking-level differences: The effect of mask duration

Abstract

Psychometric functions were obtained [from human subjects] for the interaural conditions NoSo and NoS.pi. in forward and backward masking using masks of different durations. Data were collected for the Sm, S.pi. and So conditions without an external mask. The slope parameter k and the signal level required for 76% correct detection were computed with a least-squares technique. Temporal masking and temporal masking-level differences (MLD) increased monotonically with longer mask durations. This mask-duration effect was more pronounced for forward masking than for backward masking. Without an external mask, the signal was about 3 dB more detectable in the So configuration than in the S.pi. configuration, and it was about 4 dB more detectable in the S.pi. configuration than in the Sm configuration. The psychometric functions were generally steeper for the NoS.pi. condition than for the NoSo condition in forward masking, but not in backward masking. They were also steeper for the S.pi. condition than for either the Sm or So conditions without an external mask. The temporal properties of a typical detection model consisting of a filter centered at the stimulus frequency followed by a rectifier and a final leaky integrator explained much of existent temporal masking data. Signal:500 Hz, 8 ms; interstimulus interval: 5-10 ms; mask: wide-band noise; method: 2-interval forced choice.