The signal, a 135‐Hz noise centered at 250 Hz, was partially masked by continuous wide‐band noise. The interaural correlation of both signal and masker was varied between +1.00 and zero. With a correlated masker (N0), detection is about 14 dB better with an uncorrelated signal (SU) than with a correlated signal. The masking‐level difference (MLD) diminishes as the correlation of the signal is increased to unity and as the correlation of the masker is decreased to zero. The results imply that sizable MLDs are obtained under those conditions where the addition of the signal to the noise results in adecreasein the correlation between the stimulus events at the two ears.