Patent Document ID: 8600069
Application ID: 13071712
Patent Flag: 1

Claim One:
1. A method of a multi-channel active cancellation of undesired acoustic noise in a working environment comprising: operating a random noise generator to feed a secondary disturbance to at least two control speakers; using at least two microphones to measure responses to the secondary disturbance; forming a finite impulse response of an estimated secondary path transfer function matrix (SPTFM) [ŝ] KM based upon the microphone responses; taking a Fast Fourier Transform of the finite impulse response of the estimated SPTFM [ŝ] KM to find a frequency response of the estimated SPTFM [Ŝ] KM ; calculating a mean magnitude of a main path of each column of the frequency response of the estimated SPTFM [Ŝ] KM ; dividing each column of the frequency response of the estimated SPTFM[Ŝ] KM by its respective main path mean magnitude; multiplying the matrix resulting from the dividing step by a reference value to obtain a frequency response of a virtual SPTFM[S e ] KM ; generating a reference signal correlated with the undesired acoustic noise; filtering the reference signal with the frequency response of the virtual SPTFM [S e ] KM to produce a filtered reference signal; applying a filtered-x least mean squares algorithm to the filtered reference signal and to an error feedback signal from the at least two microphones and using the result to update coefficients of an adaptive filter; filtering the reference signal using the adaptive filter to produce a cancellation signal; using the cancellation signal to drive the control speakers and thereby cancel the undesired acoustic noise correlated with the reference signal; and recursively adjusting the adaptive filter with the filtered reference signal and the error feedback signal.