A relaxed condition for "perfect" cancellation of broadband noise in 3D enclosures

This paper presents a relaxed condition for "perfect" cancellation of broad band noise in 3D enclosures. On the basis of a truncated modal model, it ca n be shown that the primary and secondary paths belong to a same subspace i f a certain condition is satisfied. There exists a finite impulse response (FIR) filter transfer function vector for perfect cancellation of the prima ry paths. The analytical result is verified numerically with an active nois e control (ANC) system in a 3D rectangular enclosure. The proposed ANC sche me is shown to fit well into the framework of an existing multichannel leas t-mean squares (LMS) algorithm for adaptive implementation. (C) 2000 Acoust ical Society of America. [S0001-4966(00)00806-7].