ABSTRACT
This chapter investigates the extent to which binaural unmasking occurs with nonsimultaneous presentation of masker and signal, particularly in forward masking. The majority of previous studies that addressed this question found that there is a substantial binaural masking level difference (BMLD) in forward masking even for fairly long signal delays, but that the amount decreases with increasing temporal separation between masker and signal. The existence of a BMLD at long delays is difficult to explain by theories of binaural interaction. A few studies, on the other hand, reported a substantial BMLD only for short delays between masker offset and signal. To further examine these conflicting findings, forward-masking curves were measured for a 10-ms 500-Hz signal in the conditions N o S o and N o S * . The masker was a bandpass frozen noise (20 Hz-1 kHz) with a duration of either 20 or 300 ms. In an additional condition, a series of frozen-noise pulses of 20-ms duration and 30-ms interpulse separation was used as the masker. A com parison of the results from the two interaural conditions showed a significant BMLD in simultaneous conditions and for the first 10-20 ms of the forward-masking curve but not for longer signal delays. Thus, the BMLD in forward masking was restricted to the short period after masker offset that corresponds to the decay time of the basilar-membrane filter at low frequencies.
