Patent ID: 6959167

Claim:
An improved echo control system including: an echo-containing near signal input; an echo canceller, coupled to a far signal reference, producing an echo estimate signal output representative of the echo contained in the near signal; a signal coupling node, coupled to the near signal input and the echo estimate signal output, producing an echo-canceled signal output having an echo residue; an echo shaping filter, coupled to the echo-canceled signal output, reducing the echo residue and providing an echo-suppressed signal output, the echo shaping filter having a spectral response determined by filter coefficients; and a background filter, coupled to: (a) an error signal representative of the difference between: (i) the echo canceled signal, and (ii) a signal representative of background filter spectral response, and (b) an adaptive control module producing a reference signal output that is a weighted sum of: (i) the echo-containing signal, and (ii) the echo canceled signal, the background filter updating the filter coefficients of the echo shaping filter responsive to a normalized least mean square (NLMS) algorithm; wherein the improvement comprises: determining, in the adaptive control module, a reference signal weight for the weighted sum, the weight being proportional to the far signal reference; and an estimate of the norm of an echo canceller error vector, and inversely proportional to en estimate of a residue of the echo canceller; and using a non-linear normalized convergence term in the NLMS algorithm.