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. . . Characteristics of forward masking by amplitude modulation
The study demonstrates a forward-masking effect of 150-ms 100% amplitude modulation (AM) on a 50-ms burst of ensuing AM imposed on the same (uninterrupted) noise carrier. In one experiment, AM forward masking was measured as a function of the temporal separation between the masker AM and signal AM. This was done to estimate the time constant of the recovery from AM forward masking. The data show that the relatively short exposure to AM substantially impairs detection of the signal AM presented immediately after the masking AM. Expressed in dB (20 log m), detection of the signal AM improves approximately exponentially with increasing masker-signal separation and reaches an asymptote within about 200 ms. The second experiment measured tuning in AM forward masking for three modulation rates of the signal AM (20, 40, and 80 Hz). Tuning of the AM forward masking was compared with that observed in simultaneous masking of AM. The data indicate that the forward-masking effect exhibits slightly sharper tuning. The results are consistent with the notion of modulation-rate selective neural channels that adapt or continue being activated beyond the offset of the masker AM. [Work supported by Grant No. DC00683 from NIDCD.]
Wojtczak, M. and Viemeister, N.F. (2004). Characteristics of forward masking by amplitude modulation. Presented at the 2004 Subjective and Objective Assessment of Sound.
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