Patent ID: 6516050
Filing Date: 2003-02-04
Classification: H04B

Abstract:
A double-talk detecting apparatus for detecting a double-talk state changed from a single-talk state, comprising:first adaptive filtering means for renewing first filter coefficients according to both a first residual signal, which is obtained from a transmission signal, indicates an echo component derived from a reception signal in the single-talk state and indicates the superposition of the echo component and a voice of a first caller in the double-talk state, and a first pseudo-echo signal, which approximates the echo component, and producing the first pseudo-echo signal from the reception signal according to the first filter coefficients renewed, the first filter coefficients deteriorating in the double-talk state; non-adaptive filtering means for producing a second pseudo-echo signal, in which a deterioration factor indicating the deterioration of the first filter coefficients renewed is included in the double-talk state, from the reception signal according to the first filter coefficients which are renewed by the first adaptive filtering means according to the first residual signal; delaying means for delaying, by a prescribed time-period, the reception signal which corresponds to a past time prior to a current time by the prescribed time-period and is input to the first adaptive filtering means, the reception signal which corresponds to the past time and is input to the non-adaptive filtering means or the transmission of the first filter coefficients renewed by the first adaptive filtering means at the past time to the non-adaptive filtering means to make the first adaptive filtering means produce the first pseudo-echo signal corresponding to the past time, to make the non-adaptive filtering means produce the second pseudo-echo signal corresponding to the past time or to produce the first filter coefficients corresponding to the past time; first subtracting means for subtracting the first pseudo-echo signal produced by the first adaptive filtering means from the transmission signal corresponding to the current or past time, which is the same as that of the first pseudo-echo signal, to produce the first residual signal, which does not have the echo component included in the transmission signal in the single-talk state, and transmitting the first residual signal to the first adaptive filtering means; second subtracting means for subtracting the second pseudo-echo signal produced by the non-adaptive filtering means from the transmission signal corresponding to the current or past time, which is the same as that of the second pseudo-echo signal, to produce a second residual signal which indicates the deterioration factor in the double-talk state and approximates the first residual signal in the single-talk state; and detecting means for detecting the double-talk state according to a difference between the second residual signal produced by the second subtracting means and the first residual signal produced by the first subtracting means.