| 摘要 |
PROBLEM TO BE SOLVED: To automatically suppress production of howling. SOLUTION: An output signal of a microphone 1 that is valid among microphones 1, 1,... is given to a plurality of band pass filters 25, 25,... in an equalizer section 24 with pass bands in different frequency bands fn (n=1, 2,..., N). A level detection section 32 receives outputs from the band pass filters 25, 25,... and compares the level of them with a predetermined reference level. A CPU 33 receives the comparison result by the level detection section 32 and the CPU 33 regards production of howling at the frequency band fn when the frequency band fn denoting a signal level higher than the reference level is in existence. Then each amplification factor of each of band amplifiers 26, 26,... in the equalizer section 24 is individually controlled so as to attenuate the signal level for the frequency band fn.
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