Contralateral and ipsilateral cueing in forward masking.

Threshold was measured for a 20-ms, 1-kHz sinusoidal signal following a narrow-band noise masker centered at 1 kHz with an overall level of 70 dB SPL. The effect of temporal uncertainty was investigated by providing a broadband, low-level noise cue, gated synchronously either with the masker intervals or the signal intervals. The cue could be either in the same ear as the signal-plus-masker, or in the opposite ear. In every case the cue produced a reduction in signal threshold, the largest reduction (about 20 dB) occurring when the cue was gated with the masker. The results indicate that in specific conditions, when the signal is similar in quality to the masker (having a similar center frequency and bandwidth), forward masking can involve a high degree os temporal uncertainty. Effects resembling "suppression" can be produced by providing a temporal cue. Adding a 1.2-kHz sinusoid at 90 dB SPL to the masker produced a 10-dB larger reduction in threshold than the noise cue. This greater effect is probably attributable to suppression of the masker by the sinusoid.