| 摘要 |
PROBLEM TO BE SOLVED: To provide a voice switch capable of accurately determining transmission and reception calls even when an acoustic echo level is large thereby always implementing optimum voice switch control. SOLUTION: The voice switch 23c first applies a correlation arithmetic operation to a transmission signal tx and a past received signal rx for a prescribed period just after start of speech to measure a bypass delay time of an acoustic echo corresponding to the received voice and set a correlation arithmetic operation object period K based on the measured delay time. Then, in the following communication period the voice switch 23c sequentially reads the received signal rx by each frame included in the correlation arithmetic operation object period K from a received signal buffer 232 while shifting the read position one sample by one sample and calculates a correlation value between the received signal rx and the transmission signal tx. Then a transmission reception state of its own terminal is determined on the basis of the correlation value and a detection result rx-flg of the received signal rx and the voice switch is controlled according to the result of determination. |
