| 摘要 |
PURPOSE:To reduce abnormal sound by providing a synchronization detection circuit detecting an amplitude of a component synchronously with a frequency of an output of a comparator of an output of a 1st low pass filter and applying an output of the synchronization detection circuit to a voltage controlled amplifier. CONSTITUTION:An input terminal is fed to a 1st LPF 1, from which only a required low frequency component is extracted. The signal is converted into a logic signal by a comparator 2 and frequency-divided by a T-FF3. Then the signal is given to a 2nd LPF 4, whose output is a sinusoidal wave. On the other hand, an output of the 1st LPF 1 is detected of its amplitude by a rectifier circuit 5 and a synchronization detection circuit 7 detects the amplitude of the component synchronously with the frequency of the output signal of the comparator 2, the output of the 2nd LPF 4 is controlled by a VCA 6 so that the amplitude is proportional to the synthesized value. Thus, the signal whose amplitude is proportional to a half of the frequency of the input signal is obtained and when it is fed to the original signal, the sound close to the original sound is obtained. |
