| 摘要 |
PURPOSE:To easily prevent the noise by amplifying the signal from the microphone by an amplifier and outputting the sound of reverse amplitude from a speaker and overlapping waves to cancel the soundwave at the time of cancelling sound. CONSTITUTION:A microphone 1 for inputting sound detects the sound near the speaker. An amplifier 2 converts the sound into the sound with the same output, phase and reverse amplitude. An output speaker 3 outputs it and cancels the sound. When the signal is plural, the additing amplification is performed. Further, when the function of cancelling the sound is improved, the degree of attenuation by each frequency between the sound transmitted inside the headphone and the sound detected by a detecting device is used as a filter in the case of a headphone and a cover like for the headphone is prepared for the sound detecting device. So as to match the phase more completely, the phase is delayed a little depending on the distance. |
