Effects of Interaural Phase Upon the Masked Threshold of Pulses

Abstract

The effect of interaural phase upon the binaural detectability of masked sine waves is well-known if poorly understood. For masking by high-level broadband noise, the tone threshold may vary by as much as 12 db, or more, depending upon interaural phase relations. Homophasic conditions are the less detectable, and antiphase conditions are the more detectable. The masking level differences (MLD's) are strongly dependent upon noise level, and they are most pronounced for tones between 100 and 500 cps.The present experiment considers the effects of interaural phase for a more complex stimulus; namely, brief periodic pulses. Binaural thresholds are measured by the Bekesy technique for four interaural conditions of signal and masking noise. Noise either in-phase or out-of-phase is used as the masking. Signal either in-phase, or with an interaural delay that produces a $-radian phase shift of all odd harmonics, is detected. Pulse rate is the parameter, and the sensation level of the masking is approximately 55 d...