| 摘要 |
<p>PURPOSE:To prevent the howling of a loudspeaker, by providing a band having a particularly large gain at the side of high band and outside the voice band to the frequency property of the system of amplification of the loudspeaker and then detecting the howling at this band to control the full frequency band of the amplification system. CONSTITUTION:The loudspeaker 1 consists of the microphone 3, preamplifier 4, volume 5, electric power amplifier 6 and speaker 7. The howling preventing device 2 is provided between the amplifier 4 and the volume 5. The device 2 includes the following component units: the equalizer 9 having the frequency property of a particularly large gain at the side of high band and outside the audible band; the level controller 10 which controls the output level of the equalizer 9 over the entire frequency band with the even attenuation quantity; the band pass filter 11 that extracts only the audible band out of the output of the equalizer 9; and the comparator 13 which transmits the control signal to the controller 10 when the output of the filter 11 exceeds the threshold level of the threshold level circuit 12.</p> |
