A method of strongly decorrelating signals comprising processing input signals to determine delay and rotation parameters which implement at least one elementary paraunitary matrix. The parameters transform the input signals into output signals with improvement in a measure of strong decorrelation. The improvement in the measure of strong decorrelation is then assessed: if it is significant the latest output signals are, designated as input signals and the process is iterated. Iteration continues until the measure of strong decorrelation ceases to improve significantly, at which point the latest output signals are designated as signals decorrelated in a wide sense.