Patent ID: 6895093

Claim:
In a communication system having a plurality of microphones at a transmitting location transmitting over separate corresponding plurality of channels to corresponding speakers in a receiving location and a plurality of microphones at the receiving location coupled over corresponding plurality of channels to speakers at the transmitting location generating echo signals, a multi-channel acoustic cancellation system comprising: filter means coupled to output of said plurality of microphones at said transmitting location and input to said plurality of speakers at receiving location for providing estimated signals representing estimates of echo path responses from said plurality microphones from said receiving location to said plurality of speakers at said transmitting location; means coupled to input of said plurality of speakers at said transmitting location and output of said microphones at said receiving location for providing true signals representing true echo signal; means for subtracting said true signals from said estimated signals to reduce echo signals and to obtain coefficient control signals representing errors; means for coupling said coefficient control signals to said filter means to change the filter coefficients to minimize said errors; and means for providing decorrelation of said signals using all-pass filters in said channels having different time varying filtering parameter; said time varying filtering parameter being a bounded random variable.