7. The speech dialogue system of claim 1, further comprising speech segment detection means for detecting a speech segment in the input signals, wherein the speech recognition means recognize the speech input from the input signals only at the speech segment detected by the speech segment detection means.
13. The speech dialogue system of claim 7, wherein the smoothing filter means includes a first smoothing filter having a first time constant and a second smoothing filter having a second time constant which is larger than the first time constant, and the switching means stops the operation of the adaptive filter means when the output power level of the first smoothing filter is below a predetermined first threshold, and starts the operation of the adaptive filter means when the output power level of the second smoothing filter is above a predetermined second threshold.