Dependence of binaural masking level differences on center frequency, masker bandwidth, and interaural parameters

Thresholds for sinusoidal signals masked by noise of various bandwidths wer e obtained for three binaural configurations: N0S0 (both masker and signal interaurally in phase), N0Spi (masker interaurally in phase and signal inte raurally phase-reversed), and NpiS0 (masker interaurally phase-reversed and signal interaurally in phase). Signal frequencies of 125, 250, 500, 1000, 2000, and 4000 Hz were combined with masker bandwidths of 5, 10, 25, 50, 10 0, 250, 500, 1000, 2000, 4000, and 8000 Hz, with che restriction that maske r bandwidths never exceeded twice the signal frequency. The overall noise p ower was kept constant at 70 dB SPL for all bandwidths. Results, expressed as signal-to-total-noise power ratios, show that N0S0 thresholds generally decrease with increasing bandwidth, even for subcritical bandwidths. Only a t frequencies of 2 and 4 kHz do thresholds appear to remain constant for ba ndwidths around the critical bandwidth. N0Spi thresholds are generally less dependent on bandwidth up to two or three times the (monaural) critical ba ndwidth. Beyond this bandwidth, thresholds decrease with a similar slope as for the N0S0 condition. NpiS0 conditions show about the same bandwidth dep endence as N0Spi, but thresholds in the former condition are generally high er. This threshold difference is largest at low frequencies and disappears above 2 kHz. An explanation for wider operational binaural critical bandwid th is given which assumes that binaural disparities are combined across fre quency in an optimally weighted way. (C) 1999 Acoustical Society of America . [S0001-4966(99)02010-X].