| 摘要 |
PURPOSE:To decrease the inversion phenomenon in switching a gate circuit by providing a filtering part extracting individually a pulse noise and a signal component from an audio signal and an automatic gain control section controlling individually the gain of the amplifying part detecting the pulse noise based on each output signal of the filtering part. CONSTITUTION:When a frequency in the input signal VS1 of a gate circuit 1 is fS1, the detection level of the pulse noise of the detection level of the pulse noise is VD1 and the pulse noise generated in the inversion phenomenon is controlled so as not to be switched. When the input level of the audio signal is increased from the level VS1 to VS2, the noise detection level is increased from the level VD1 to the level VD2 so as to remove the noise to a slightly large noise than the level VS1. Then increasing the frequency of the audio signal from fS1 to fS2, the detection level at the input level VS1 from the fS1 to fS2, the detection level at the input level is increased from VD1 to VD1' so as not to detect a small noise. Thus, the inversion phenomenon is blocked even to the change in the frequency and amplitude of the signal.
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