AUDIO EQUIPMENT INCLUDING MEANS FOR DE-NOISING SPEECH SIGNAL BY FRACTIONAL DELAY FILTERING, IN PARTICULAR FOR 'HANDS-FREE' TELEPHONY SYSTEM

摘要

PROBLEM TO BE SOLVED: To reduce noise effectively so as to deliver to a remote speaker a voice signal that is representative of speech uttered by a near speaker.SOLUTION: The equipment comprises two microphones, sampling means, and de-noising means. The de-noising means is non-frequency noise reduction means comprising a combiner having an adaptive filter performing an iterative search to cancel the noise picked up by one of the microphones on the basis of a noise reference given by the other microphone sensor. The adaptive filter is a fractional delay filter modeling a delay that is shorter than the sampling period. The equipment also has voice activity detector means delivering a signal representative of the presence or the absence of speech from the user of the equipment. The adaptive filter receives this signal as input so as to enable it to act selectively: either i) to perform an adaptive search for the parameters of the filter in the absence of speech, or else ii) to "freeze" those parameters of the filter in the presence of speech.