| 摘要 |
PURPOSE:To increase a low-pass area without resulting deterioration in sound quality, and normal feeling, by deriving nearly a sine wave having the frequency of the half of the frequency of an output from a filter, and adding it on its original acoustic signal. CONSTITUTION:At the time of supplying the acoustic signal from a band-pass filter 16 to a frequency and voltage conversion circuit 17, and deriving a DC voltage corresponding to the frequency, a voltage controlled oscillation circuit 18 derives a signal having an oscillation frequency with the sine wave corresponding to the voltage. The frequency/voltage conversion circuit 17, and the voltage controlled oscillation circuit 18 oscillate in the frequency of the half of the output frequency of the band-pass filter 16 working with each other. A muliplication circuit 19 multiplies the signal generated from the voltage controlled oscillation circuit 18 by the output from an envelope detection circuit 20, and supplies a result to an adder circuit 13. Thereby, it is possible to perform the reproduction of sound including no higher harmonic and few distortion, and also, to prevent the deterioration in the sound quality, and the normal feeling.
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