Patent ID: 6246760
Filing Date: 2001-06-12
Classification: H04M

Abstract:
A subband echo cancellation method for a multichannel teleconference in which received signals of plural channels are reproduced as acoustic signals by loudspeakers corresponding to said plural channels, said acoustic signals being received by at least one microphone after propagating over each echo path thereto, an echo replica being subtracted from an echo provided from said at least one microphone, an echo cancellation error signal resulting from said subtraction and said received signal of each of said plural channels being used to calculate an adjustment vector, said adjustment vector being used iteratively to adjust an estimated value of an impulse response of each echo path, estimated echo paths having said adjusted impulse response being generated for each of said echo paths, and the corresponding one of said received signals being applied to each estimated echo path to generate said echo replica, the method further comprising the steps of:(a) dividing said received signal and said echo into N subbands in each of said plural channels, and decimating them with predetermined decimation rates, respectively, to generate N subband received signals and N subband echoes, N being an integer equal to or greater than 2;(b) generating N echo replicas by providing said N subband received signals to N estimated echo paths, each formed by a digital filter having a filter coefficient of a predetermined number of taps which simulates the impulse response of said echo path in each of said N subbands;(c) subtracting said N echo replicas from corresponding N subband echoes to generate echo cancellation error signals in said N subbands;(d) iteratively adjusting said filter coefficients of said digital filters in a manner to minimize said N echo cancellation error signals on the basis of said N echo cancellation error signals and corresponding N subband received signals; and(e) combining said echo cancellation error signals in said N subbands into a full band send signal having said echoes suppressed; and(f) extracting a variation component of the cross-correlation between said received signals of said channels as said adjustment vector.