Symmetry properties of binaural masked detection thresholds with respect to the dependence on interaural time delay and interaural amplitude ratio of the masker

Abstract

Thresholds for a 500-Hz tone masked by broad-band random noise were measured for conditions that simultaneously include differences in the interaural amplitude ratio and in the interaural time delay of the masking noise. The interaural amplitude ratio of the target was always equal to the interaural amplitude ratio of the masker, and the interaural phase of the target always differed by 180° from the interaural phase of the masker. Measurements include interaural time delays of both polarities for each of five amplitude ratios between 0 and 40 dB. The time delay values were ±200 μsec, ± 500 μsec, and ± 800 μsec. The thresholds for positive and negative values of delays do not differ more than experimental error for any amplitude ratio. It is argued that this symmetry in detection performance, with respect to the sign of the delay, is unexpected in light of the asymmetry observed in interaural time discrimination results [Domnitz, J. Acoust. Soc. Am. 53, 1549–1552 (1972)] and that the results of these two experiments may have important implications for the interaction of time delay and amplitude ratio in binaural hearing models.