| 摘要 |
PURPOSE:To suppress howling generation by supplying a signal which is inputted from a microphone to a band elimination filter which changes a characteristic sequentially through an amplifier, and by supplying a filter output to a speaker through the amplifier. CONSTITUTION:A signal which is inputted from a mike 1 is supplied to an attenuator 6 through an amplifier 2, and an output of the device 6 is supplied to a speaker 4 through an amplifier 3. The signal which is inputted to the device 6 is sent to digital filters 8-1 and 8-2 through an AD converter 7. The filters 8-1 and 8-2 can change a filter characteristic without accompanying a phase change, and they are constituted of a delaying-circuit group 9, a multiplier 10 and an adder 11. The coefficient which gives the characteristic of the filter is stored in coefficient memories 13-1 and 13-2, and by this coefficient, a BEF is realized. The coefficient is read by random address generating circuits 14-1 and 14-2, and a timing generating circuit 15, and the howling generation can be suppressed by changing the filter characteristic sequentially. |
