| 摘要 |
PURPOSE:To reduce noise quickly and over a wide frequency range by extracting signal at a specified frequency on the basis of electric signal for sensing noise, delaying and inverting this signal, and generating sound in the opposite phase to the noise. CONSTITUTION:The phase characteristic of noise is controlled by a control circuit 17 on the basis of electric signals from a microphone 15 as a noise sensing and converting means, and sounds in the opposite phase to the noise from a speaker 16 as a sound generating means is generated to achieve reduction of the noise. The control circuit 17 is in series connected with a preamplifier 18 in connection with the microphone 15, analog filters 19, 23, 27 as extracting means, delay circuits 20, 24, 28 as signal delay means, phase inverter circuits 21, 25 as signal inverting means, and power amplifiers 22, 26, 29. Thereby signal processing by control circuit 17 is performed in a short time, and noise reduction is made over a wide frequency range. |
