| 摘要 |
PURPOSE:To prevent the howling and then ensure a control of the sound volume by the voltage proportional to the degree of noise, by providing the compounding circuit for each aural output and then giving a comparison between the output of the compounding circuit and the output compounded by the microphone provided in the room of the car by a differential amplifier. CONSTITUTION:The mike 1 picks up the ambient noise as well as the sound delivered through the speaker of the mobile sound device 6, and these sound and noise are detected by the wave detector 2. If the position of the mike 1 provided in the room of the car is not at the center between (a) and (b), a control is given to the resistance (e). The same control is given by the resistance (f) to the position between (c) and (d). The output obtained through the compounding of (a) and (b) plus (c) and (d) is controlled by the variable resistance 8 and according to the position before and after the mike 1 and then detected the wave detector 4. This detected aural output is supplied to the reversed side of the differential amplifier 3, and thus the aural signal picked up by the mike 1 is eliminated to produce the output proportional to the noise. With the quantity of this output, a control is given to the voltage sound volume variable device 5. |
