| 摘要 |
PURPOSE:To surely make a radiated tone from a cavity silent by controlling a control sounding device by a time waveform signal being the result of each frequency component analyzed by a frequency analyzer processed by using a coefficient of a corresponding frequency read from a storage device and synthesized. CONSTITUTION:A sound generated by a sound source 13 is converted into an electric signal by a microphone 15, amplified by an amplifier 17, converted into a digital signal by an A/D converter 18 and the frequency is analyzed by a high speed frequency analyzer 19. On the other hand, a phase and a multiple factor in response to the sound wave mode pattern with respect to each frequency of the cavity 12 are stored in a storage device 20 and when each frequency component is outputted to the high speed frequency analyzer 19, an arithmetic unit 21 multiples the coefficient and the signal is restored to the time waveform and the result is given to a speaker 19 via a D/A converter 22 and an amplifier 23. Thus, the sound from a sound source 13 and a sound from the speaker 16 are cancelled completely at a control object point 14. Thus, the sound is surely erased. |
