Electrical audio signal processing systems and devices – Acoustical noise or sound cancellation – Adjacent ear
Patent
1993-09-24
1995-04-25
Isen, Forester W.
Electrical audio signal processing systems and devices
Acoustical noise or sound cancellation
Adjacent ear
G01K 1116
Patent
active
054106079
ABSTRACT:
An apparatus for reducing noise radiated from a complex vibrating surface includes: a motion sensor responsive to a region of the vibrating surface that contributes to a noise field in a fluid medium; a controller having a substantially fixed transfer function, where the controller is responsive to an electrical motion signal produced by the motion sensor and is operative to produce an electrical antinoise signal; and an acoustic driver responsive to the electrical antinoise signal and operative to produce and an acoustic antinoise field that is substantially 180.degree. out-of-phase with the original noise field. The antinoise field reduces the original noise field by the process of destructive interference without substantially affecting the motion of the vibrating surface. If the medium is air, the acoustic driver is preferably a loudspeaker which is operated so that its cone velocity is approximately equal to the ratio of a noise-source area weighting to a cone area weighting multiplied by the velocity of the noise source. A method for reducing noise radiated from a complex vibrating surface in accordance with the present invention includes: dividing the vibrating surface into a plurality of regions, each of which contributes to a noise field in a fluid medium; and, for each region of the vibrating surface, developing an antinoise field that effectively reduces the original noise field associated with that region. The plurality of antinoise fields provides wideband noise reduction in a quiet zone of arbitrary size and shape.
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Mason V. Bradford
Naghshineh Koorosh
Isen Forester W.
SRI - International
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