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Bandlimiting anti-noise in personal audio devices having adaptive noise cancellation (ANC)

  • US 8,948,407 B2
  • Filed: 12/21/2011
  • Issued: 02/03/2015
  • Est. Priority Date: 06/03/2011
  • Status: Active Grant
First Claim
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1. A personal audio device, comprising:

  • a personal audio device housing;

    a transducer mounted on the personal audio device housing for reproducing an audio signal including both source audio for playback to a listener and an anti-noise signal for countering effects of ambient audio sounds in an acoustic output of the transducer;

    a reference microphone mounted on the housing for providing a reference microphone signal indicative of the ambient audio sounds;

    an error microphone mounted on the housing in proximity to the transducer for providing an error microphone signal indicative of the acoustic output of the transducer and the ambient audio sounds at the transducer; and

    a processing circuit that implements an adaptive filter having a response that generates the anti-noise signal from the reference microphone signal to reduce the presence of the ambient audio sounds heard by the listener, wherein the processing circuit shapes the response of the adaptive filter in conformity with the error microphone signal and the reference microphone signal by adapting the response of the adaptive filter to minimize the ambient audio sounds at the error microphone, wherein the response of the adaptive filter is further adjusted independent of the reference microphone signal and independent of the source audio by altering an input to a coefficient control block of the adaptive filter to constrain the adaptive filter to alter the adapting of the adaptive filter to the ambient audio sounds, and wherein the response of the adaptive filter is adjusted independent of the reference microphone signal and the source audio by combining injected noise with the input to the coefficient control block so that the response of the adaptive filter is biased by the coefficient control block adapting to attenuate frequencies present in the injected noise, whereby the response of the adaptive filter is reduced in frequency regions in a frequency range of the injected noise.

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