The effect of phase and pressure‐level differences on the detectability of single‐frequency signals in the presence of noise is presented for listening over of a binaural transmission system. During the several tests to be described, the two microphones were supported in free space both in the absence and in the presence of various approximations to an artificial head. The results indicate that over‐all detectability is a function of the combined binaural phase relationships of both signal and noise and of the monaural intensity relationship of the two signals at the ear having the higher signal to noise ratio. Some indication was found that phase differences may influence detectability to frequencies as high as 2000 cps. Pressure‐level differences, on the other hand, decrease in magnitude with decreasing frequency until only a small effect remains at 250 cps.