Noise-level adaptive residual echo suppressor
AssigneeScanSoft, Inc.
InventorWouter Dehandschutter
Life of this patent
Estimating the term…
Abstract
An improved echo control system has an adaptive controlled echo canceling filter arrangement in which a background filter updates the filter coefficients of an echo shaping filter responsive to a normalized least mean square (NLMS) algorithm. An adaptive control module determines a weighted reference signal for the background filter in which the weight is proportional to a 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 a non-linear normalized convergence term is used in the NLMS algorithm.
Claims16
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.
An improved method of echo control including:
- providing an echo-containing near signal input;
- producing, with an echo canceller coupled to a far signal reference, an echo estimate signal output representative of the echo contained in the near signal;
- producing, with a signal coupling node coupled to the near signal input and the echo estimate signal output, an echo-canceled signal output having an echo residue;
- reducing, with an echo shaping filter coupled to the echo-canceled signal output, the echo residue and providing an echo-suppressed signal output, the echo shaping filter having a spectral response determined by filter coefficients;
- and
- providing 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 back ground 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.
Dependencies are inferred from the claim text.