| 摘要 |
PURPOSE:To improve remarkably the detection capability by expressing a characteristic representing an echo path at a region subject to orthogonal transformation, dividing the band, applying processing independently at each band and detecting the 2-way talking to the result of orthogonal transformation. CONSTITUTION:A reception signal x(n) is inputted from a terminal 1, inputted to a low frequency echo cancel section 101 and a high frequency echo cancel section 102, and only a high frequency component X2(i,n) among the frequency components of the signal x(n) is outputted from a partial DFT circuit 112. A signal y(n) is also inputted to the low frequency echo cancel section 101 and the high frequency echo cancel section 102 and the partial DFT circuit 122 outputs only the high frequency component Y2(i,n) only. The high frequency echo cancel section 102 erases echo to the high frequency component similarly and a signal e2(n) obtained by applying IDFT to a residual E2(i,n) is given to a partial sum 142 and the sum with an output from the low frequency echo cancel section 101 is taken. The 2-way talking is detected by the high frequency echo cancel section 102 and the low frequency echo cancel section 101 respectively to attain the detection of 2-way talking with high sensitivity.
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