| 摘要 |
PURPOSE:To reproduce a sound with abundant sound quality by adding a harmonic of an in-band signal with a proper level to an acoustic signal when the acoustic signal whose band is limited to a definite band is reproduced. CONSTITUTION:Envelope detectors 11-3, 11-4 detect a harmonic output whose frequency is high (at output terminals 6, 7), the detection output is smoothed respectively by integration circuits 15-3, 15-4, the smoothed output is fed to gain control amplifiers 16-3, 16-4, the output of the gain control amplifier 16-3 is fed to an inverting input of operational amplifiers 17, 18, 19 and the output of the gain control amplifier 16-4 is fed to a noninverting input of the operational amplifiers 17, 18, 19, the operational amplifiers 17, 18, 19 output a control signal to gain control circuits 10-1, 10-2, 10-3, which control the gain of harmonic signals from BPFs 9-1,9-2,9-3 whose center frequencies are respectively 2fH1, 2fH2, 2fH3 to control the harmonic signals based on the acoustic signal whose frequency band is limited as f<=fc thereby adding the harmonic component with a proper level to the acoustic signal. |
