1. A method of processing a multichannel signal, said method comprising: for each of a plurality of different frequency components of the multichannel signal, calculating a difference between a phase of the frequency component in a first channel of the multichannel signal and a phase of the frequency component in a second channel of the multichannel signal; and based on information from the plurality of calculated phase differences, calculating a value of a coherency measure that indicates a degree of coherence among the directions of arrival of at least the plurality of different frequency components.