| 摘要 |
PROBLEM TO BE SOLVED: To alter amplitude/phase characteristics of a diffracted sound itself of a noise source by changing a sound proof barrier itself with an active silencing device into a cylindrical or rectangular duct etc., and to uniformly and securely reduce the diffracted sound of the sound proof barrier circumferentially along the barrier with one pair of a controller and a microphone even when a plurality of speakers are used. SOLUTION: The sound proof barrier with the active silencing device comprises a line sound source speaker 2 for control which is installed at or nearby a tip part of the sound barrier 1 and has equal-amplitude and in-phase line sound source characteristics and a point sound source group 3 for control constituted by arranging a plurality of point sound source speakers 3a apart circumferentially along the barrier so that one speaker in every half wavelength, a reference microphone 4 which is installed inside the sound barrier 1 nearby its upper end and detects the sound pressure of the noise source, a microphone 5 for control which is installed outside the sound barrier 1 nearby its upper end and detects the sound pressure of the diffracted sound, and a control unit 6 which adjusts the amplitude and phase of the speaker 2 or 3 with a signal detected by the reference microphone 4 and minimizes a signal detected by the microphone 5 for control. COPYRIGHT: (C)2006,JPO&NCIPI
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