A method of adjusting an ANC system is disclosed in which a microphone is acoustically coupled to a loudspeaker via a secondary path and the loudspeaker is electrically coupled to the microphone via an ANC filter. The method includes measuring phase characteristics of the secondary path in various modes of operation； determining from the measured phase characteristics a statistical dispersion of the phase characteristics in the various modes of operation； determining from the statistical dispersion a minimum phase margin； adjusting the ANC filter to exhibit in any one of the modes of operation phase characteristics that are equal to or greater than the minimum phase margin； and adjusting the ANC filter to exhibit in any one of the modes of operation amplitude characteristics that are equal to or smaller than a maximum gain margin.
