Method And Device For Variable Pitch Echo Cancellation

Abstract: The processing of a signal y(t) from a microphone (MIC) of a device further comprising at least one loudspeaker (HP) intended to be powered by a signal x(t) aims to limit an echo effect induced by the microphone (MIC) picking up a sound emitted by the loudspeaker (HP) in the surroundings of the device. Said sound emitted by the loudspeaker (HP) and any acoustic reflections thereof follow an acoustic path w from the loudspeaker (HP) to the microphone (MIC). In order to limit the echo effect, the processing comprises determining s(t) a useful signal s(t) by subtracting from the signal y(t) from the microphone (MIC) a given estimate of an echo signal x(t) * w(t) by applying a filter w(t) to the loudspeaker power supply signal x(t). The filter w(t) is adaptive by variable pitch to account for a change in the acoustic path w(t) over time. Since the loudspeaker power supply signal x(t) is obtained in the form of a time sequence of frames of signal samples, the adaptive filter w(t) is produced at each frame k of samples according to an update ?W(k) of the acoustic path w for said frame k and by applying a normalisation ? satisfying a selected criterion for minimal variance, the normalisation ? being a function of a parameter representative of a statistical expectation of the useful signal s(t).

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