A method of processing signals in a hearing aid system (200, 300) comprises the steps of transforming two audio signals to the time-frequency domain, calculating the interaural coherence, deriving a first gain based on the interaural coherence, applying the first gain value in the amplification of the time-frequency signals, and transforming the signals back into the time domain for further processing in the hearing aid. The first gain value as a function of the value representing the interaural coherence comprises three contiguous ranges for the values representing the interaural coherence, where the maximum slope in the first and third range are smaller than the maximum slope in the second range, the first range comprising low interaural coherence values, the third range comprising high interaural coherence values, and the second range comprising intermediate interaural coherence values. The invention further provides a hearing aid system (200, 300) adapted for suppression of interfering speakers.