| 摘要 |
PROBLEM TO BE SOLVED: To inexpensively and securely prevent the input of background sound at the periphery of a telephone set. SOLUTION: Transmitting sound inputted to a handset 25 is converted into a digital signal by a CODEC circuit 26. Background sound detected by a microphone 37 which is installed independent of the handset 25 is converted into the digital signal by an A/D converter 38 and is inputted to a digital filter 39. A subtraction means 40 subtracts the output of a digital filter 39 from the output signal of the CODEC circuit 26 and a filter coefficient update means 41 receiving the subtracted result updates the filter coefficient of the digital filter 39 in accordance with a prescribed algorithm so that only a sound component obtained by removing a background sound component contained in the transmitting signal from the transmitting signal is outputted from the subtraction means 40. |
