Spectral interference in a binaural detection task: effects of masker bandwidth and temporal fringe.

Recently, it was reported that the detectability of a 100-ms, 800-Hz tone (the target) presented antiphasically (S pi) against a background of continuous, broadband, diotic noise could be degraded if a 400-Hz tone (the interferer) was gated simultaneously with the target [L. R. Bernstein, J. Acoust. Soc Am. 89, 1306-1313 (1991)]. This degradation, termed "interference," was reduced by presenting the interferer continuously. In the present study, the amount of such interference was measured when the target was masked by either a broadband or a narrow-band (100-Hz-wide) noise. The narrow-band noise produced a relatively large masking-level difference, thereby allowing about 10 dB of interference to be observed. In other conditions, the interferer was turned on (temporally "fringed") prior to the target. The presence and duration of a forward fringe of the interferer did not reduce the interference, even for forward fringes of 320 ms. This result is consistent with those of Woods and Colburn [W. S. Woods and H. S. Colburn, J. Acoust Soc. Am. 91, 2894-2902 (1992)] who measured the detectability of interaural delay of low-frequency tones. The data from both studies indicate that binaural interference is observed even under conditions where interferers and targets are perceptually segregated in the sense that listeners hear more than one sound object.