1. Method for separating a mixture of source signals to regain said source signals, said method being based on measured signals, characterized in, that every measured signal is brought to a separation structure comprising cross connected linear filters and subsequent adders, that cross correlation functions between the signals after said adders are calculated for delays k between a first delay K 1 and a last delay K 2, that a criterion function is used to determine how the linear filters comprised in said separation structure will be designed in every real situation, that said criterion function is formulated as a sum of terms where the addition is extended to all possible cross correlation functions between the output signals of separation structure at all possible delays (k) between K 1 and K 2, and that each term in said sum has a weight factor and another factor consisting of an even function, f, of a specific cross correlation function at a specific delay.