Two experiments compare the effect of fixed and random phase relations between masker and signal in binaural masking. In Experiment 1, a comparison made between interaural time delay and phase shift of a narrow‐band‐noise signal where the phase relations between the signal and the masker are random. The signal is Gaussian noise passed through a 50‐cps filter centered at 500 cps. The masker is broad‐band noise from a second noise generator. The conditions using noise as the signal are compared with the same conditions in which a 500‐cps tone is the signal. A two‐interval, forced‐choice procedure was used to obtain MLD's (masking‐level differences). The MLD increases rapidly as the interaural phase shift or interaural time delay increases. The MLD's for corresponding phase‐shift and time‐delay conditions are approximately the same for tonal and noise signals. In Experiment 2, a single noise generator is used and a comparison is made between N0 S0 and N0 Sπ for various phase relations between the narrow‐band‐noise signal and the masker. The noise signal has the same bandwidth as in Experiment 1. The results show a substantial dependence of the MLD's on the signal‐noise phase relation.

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