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Active attenuation of noise in a closed structure

  • US 4,562,589 A
  • Filed: 12/15/1982
  • Issued: 12/31/1985
  • Est. Priority Date: 12/15/1982
  • Status: Expired due to Term
First Claim
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1. A system for the attenuation of sound waves produced in a closed structure having walls, an exterior surface and an interior by a source of sound waves exterior to said closed structure, comprising:

  • input sensing means disposed adjacent said exterior source of sound waves, said sensing means being operable to produce electrical signals representing the amplitude and phase characteristics of said exterior sound waves, said exterior sound waves impinging against said exterior surface of said closed structure in a pattern and inducing vibration of said walls to produce sound waves in the interior of said body;

    cancelling means for generating cancelling sound waves of corresponding amplitude and 180°

    out-of-phase with said exterior sound waves;

    waveguide means disposed in the interior of said closed structure immediately adjacent said wall of said closed structure in the area of impingement of said exterior sound waves, and being spaced from said sensing means, said waveguide means being connected to said cancelling means to provide a path for the propagation of said cancelling sound waves to said closed structure wall for combination with said exterior sound waves;

    error sensing means disposed within said interior of said closed structure and being spaced from said waveguide means, said error sensing means being operable to produce electrical signals representing the amplitude and phase characteristics of said combination of said exterior sound waves and cancelling sound waves at said closed structure wall; and

    electronic controller means connected with said input sensing means, cancelling means and error sensing means, said electronic controller means being operable to process said electrical signals from said input sensing means, produce outputs for driving said cancelling means to produce said cancelling sound waves, and to adjust said outputs based on said electrical signals from said error sensing means for the production of revised outputs for driving said cancelling means.

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