“…Techniques in the first class reduce the leakage components in the noise references i) by using a more robust fixed blocking matrix design [7]- [10], ii) by using an adaptive blocking matrix [11]- [13], or iii) by constructing a blocking matrix based on estimating the ratios of the acoustic transfer functions from the speech source to the microphone array [6], [14], [15]. Techniques in the second class limit the distorting effect of the leakage components i) by controlling the step-size of the multichannel adaptive algorithm, such that the multichannel ANC is only updated during periods 1558-7916/$31.00 © 2013 IEEE (and for frequencies) where the signal-to-noise ratio is low [6], [7], [11]- [13], [16]- [18], ii) by constraining the update formula for the multichannel adaptive filter [9], [12], [19], [20], or iii) by taking speech distortion due to speech leakage into account using a speech distortion weighted multichannel Wiener filter [21], [22]. In practice, several of these techniques are usually combined.…”