Abstract: A reception signal is input to an echo generator system. An observation signal is gathered from the system. The reception signal is filtered to produce an echo prediction signal. The echo prediction signal is subtracted from the observation signal to produce an error signal. The observation signal is decomposed into M spectral components relating to different frequencies of the spectrum. M corresponding spectral components of the echo prediction signal are obtained. M quantities, each having a value with progressive variation representative of a degree of similitude between, respectively, one of the M spectral components of the observation signal and the corresponding spectral component of the echo prediction signal, are calculated. At least one spectral shaping of the error signal is carried out as a function of these M calculated quantities so as to adapt the filtering and/or to deliver the output signal from the echo canceller.

Abstract: The echo canceller is designed to be placed between a hands-free acoustical interface and a communications network. It comprises a plurality of processing paths connected in parallel and each allocated to one of a plurality of adjacent sub-bands taken from the spectrum band of the output signal. Each path comprises an analysis filter receiving the echo-containing signal for transmission after correction, a second analysis filter receiving the incoming signal coming from the network, and feeding an adaptive filter that supplies an estimated echo in the respective sub-band to the subtractive input of the subtracter and a synthesis filter. The adaptive filters in at least some of the sub-bands implement a QR decomposition RLS algorithm on the incoming signal, using the fast version thereof, with or without recursive order.

Abstract: The echo canceller comprises an adaptive filter receiving the coefficients of a direct discrete transform into the frequency domain, computed on successive blocks of an input signal and fed via an inverse transform circuit to the subtractive input of an adder for forming an output signal going to the network, and an adaptor circuit for adapting the coefficients of the filter. The adaptor circuit receives the coefficients of successive transforms of blocks of output signal samples via a noise reducer.