Patent ID: 8090094

Claim:
An echo canceller comprising: an adaptive filter which generates a pseudo echo signal in accordance with a far-end input signal; an echo cancellation means which subtracts the pseudo echo signal from a near-end input signal; a tone-kind judgment means which judges whether the far-end input signal is a predetermined kind of tone signal or not, said tone-kind judgment means when judging that the far-end input signal is a predetermined kind of tone signal, also detecting an end of the tone signal; an echo-cancellation-amount calculation means which calculates an amount of echo cancellation of a signal output from the echo cancellation means; and an at-tone-input coefficient control means which causes the adaptive filter to stop update of a coefficient of the adaptive filter in accordance with satisfaction of a predetermined condition for the amount of echo cancellation, when the tone-kind judgment means judges that the far-end input signal is the predetermined kind of tone signal, the at-tone-input coefficient control means comparing amounts of echo cancellation before and after timing that the tone-kind judgment means judges to be the end of the tone signal, in accordance with a result of the comparison, causing the adaptive filter to restart the update of the coefficient after resetting the coefficient of the adaptive filter, or forcefully causing the adaptive filter to restart the update of the coefficient without resetting the coefficient of the adaptive filter, including forcefully causing the adaptive filter to restart the update of the coefficient without resetting the coefficient of the adaptive filter, if a conditional expression, Δ2<ACANC(n+1)<ACANC(n)−Δ1 holds, and causing the adaptive filter to restart the update of the coefficient after resetting the coefficient of the adaptive filter, if another conditional expression, ACANC(n+1)<Δ2 holds, where ACANC(n) and ACANC(n+1) denote the amounts of echo cancellation before and after timing that the tone-kind judgment means judges to be the end of the tone signal respectively, and Δ1 and Δ2 denote predetermined threshold values respectively.