| 摘要 |
PURPOSE:To prevent a residual echo which can not be erased by an echo canceler from being misdecided as sound presence by a sound detector used for transmission system. CONSTITUTION:After an offset addition part 17 adds a DC offset to a transmission-side signal according to the signal intensity of a reception-side signal found by a signal intensity calculation part 16, a zero-cross frequency calculation part 18 calculates the frequency of zero crossing. An echo detection part 19 decides whether or not the transmission-side signal contains the echo component of the reception-side signal according to whether the frequency of zero crossing is large or small and when the echo detection part 19 decides the presence of the echo, the output of the sound detector is made soundless, so the sound detector which never misdecides the residual echo, which can not be removed by the echo canceler, as the sound presence is obtained. |
