| 摘要 |
PURPOSE:To block the generation of howling by inserting a phase fluctuation circuit and a variable gain amplifier circuit controlled by an output of a control signal generating circuit in a system forming an acoustic loop. CONSTITUTION:A microphone 1 collecting mainly the voice of the sound source aud a microphone 7 collecting mainly speaker sound are used in an acoustic equipment having sound collection and reproducing system and the quantity of the signal level inputted to both is compared to control the variable gain amplifier circuit. Thus, the stable variable gain control is attained independently of the quantity of sound volume level in the sound field. Moreover, the phase fluctuation circuit 5 is provided to give a slow fluctuation to the phase of the sound wave radiated from the speaker thereby preventing the resonance of the sound wave only having a specific wavelength in the sound field, then no howling is caused and the output of the maximum sound volume level outputted by the accoustic equipment is obtained in the range where the feedback loop gain does not exceed the unity. |
