Binaural unmasking behavior was investigated at suprathreshold levels using 250‐ and 500‐Hz sinusoids. First, the traditional detection masking‐level difference (MLD) was measured; then a loudness balance was made between the masked S0 and Sπ signals at four sensation levels to infer the superthreshold binaural advantage. The results showed that the antiphasic advantage decreased with the increasing sensation level of the signals and implied that the loudness of the masked antiphasic signals grew more slowly than that of the masked homophasic signals. The influence of this loudness effect on other data in the literature is discussed.