| 摘要 |
PROBLEM TO BE SOLVED: To eliminate noise by arranging a porous material in the air flow and generating a sound of reverse phase for a noise generated from an apparatus thereby canceling the noise. SOLUTION: In a body frame 105, contaminated air is purified through a dust collecting section 100 and a fan 200 to produce clean air. In the dust collecting section 100, dust being charged by a corona discharge beam 101 is captured by a dust collection plate 102. When the air is passed through the dust collecting section 1O0 by means of the fan 200 comprising a rotary machine 201 and a rotary blade 202, noise is generated and picked up through a microphone 1. A phase modulator 2 modulates the phase of a sound wave detected by the microphone 1 at an appropriate timing and the modulated sound wave is delivered from a speaker 4 through a voice generator 3. Sounds from the air and the speaker pass through the porous material 10 arranged in the air path along with noise. They are combined effectively through sound wave interference and the sound level of combined sound wave approaches zero. |
