Masking with interaurally delayed stimuli: the use of "internal" delays in binaural detection.

Detectability of 500-Hz tones was measured in the presence of broadband masking noise using three types of binaural conditions. In the first, the masker was presented diotically and the tone was interaurally delayed. In the second, the masker was interaurally delayed and the 500-Hz tone was presented either in phase (S0) or out of phase (S pi). In the third, the masker consisted of the sum of two independent noises having interaural delays of equal magnitude and opposite sign. The signal was, once more, presented either in phase (S0) or out of phase (S pi). Comparisons among the data and quantitative analyses assuming the use of compensatory "internal delays" suggested that internal delays are operative and compensate accurately for external delays of up to approximately 750 microseconds. The analyses also indicated that larger internal delays (i.e., up to 2 to 3 ms) are probably also operative. However, performance using such large internal delays appears to be degraded in accord with the hypothesis that their application introduces "noise" in the internal representation of the stimuli.