Masking Level Differences Obtained with Pulsed, Tonal Maskers

Abstract

Bursts of tonal signals (125 msec) were masked by tones of the same duration and frequency. The masker was always diotic, while the signal was either diotic (a homophasic condition) or reversed in phase to one ear (an antiphasic condition). MLD's, the differences in detection between homophasic and antiphasic conditions were measured for signals of three frequencies, 250, 500, and 1000 Hz. The phase between signal and masker was set at 0°, 45°, 90°, or 135°; MLD's obtained for these conditions of signal-to-mask phase were 2, 2, 17, and 8 dB, respectively. In addition, MLD's were slightly higher for the higher frequencies. In the psychophysical procedure used, mask alone was followed by mask alone or signal plus mask, and subjects responded “SAME” or “DIFFERENT.” The interaural differences of time and intensity necessary for detection in the antiphasic conditions were considerably larger than those to be expected from other measures of lateralization.