| 摘要 |
PURPOSE:To stop the operation of an echo controlling device, by providing a band dividing circuit, frequency variation detecting circuit, level variation detecting circuit, signal detecting circuit, and deciding circuit and detecting a non- sound signal which does not send out any conditioning tone. CONSTITUTION:An input signal is divided into plural frequency bands by a band divider 12 and frequency variation of the input signal of each band is detected by a frequency detecting circuit 13. Moreover, variation of the level of the input signal of each band is detected by a level variation detecting circuit 14 from the output of the circuit 12. Furthermore,existence of the input signal of each divided band is detected by a signal detecting circuit 15 from the output of the circuit 12. Finally, whether an input signal is a sound signal or non-sound signal is decided 16 from the output of the circuits 13, 14, and 15 and a signal which stops the operation of an echo controlling device is outputted. |
