Masking with interaurally delayed stimuli: The use of "internal" delays inbinaural detection

Detectability of 500-Hz tones was measured in the presence of broadband mas king noise using three types of binaural conditions. In the first, the mask er was presented diotically and the tone was interaurally delayed. In the s econd, the masker was interaurally delayed and the 500-Hz tone was presente d either in phase (S0) or out of phase (S pi). In the third, the masker con sisted of the sum of two independent noises having interaural delays of equ al 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 quant itative analyses assuming the use of compensatory "internal delays" suggest ed that internal delays are operative and compensate accurately for externa l delays of up to approximately 750 mu s. 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 degrad ed in accord with the hypothesis that their application introduces ''noise' ' in the internal representation of the stimuli. (C) 1999 Acoustical Societ y of America. [S0001-4966(99)03001-5].