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Variable gain active noise cancelling system with improved residual noise sensing

  • US 7,103,188 B1
  • Filed: 03/08/1999
  • Issued: 09/05/2006
  • Est. Priority Date: 06/23/1993
  • Status: Expired due to Fees
First Claim
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1. An active noise canceling system comprising:

  • a sound generator, responsive to drive signals applied thereto, for generating an anti-noise field;

    a noise cancellation processor, for generating the drive signals to the sound generator;

    a first sound sensor disposed within said anti-noise field to generate a residual signal indicative of the sum of ambient sounds and anti-noise impinging on the sensor, wherein said noise cancellation processor processes the residual signal to form a component of the anti-noise field; and

    means for generating indicia of the level of ambient noise and responsively varying a transfer function of the system in response to said indicia of amplitude of ambient noise such that a gain of the transfer function of the system is decreased in response to a decrease in said indicia of amplitude of ambient noise, wherein the transfer function comprises a ratio of an output signal of the noise cancellation processor to at least the residual signal.

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