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Apparatus and method for canceling acoustic echoes including non-linear distortions in loudspeaker telephones

  • US 5,680,450 A
  • Filed: 02/24/1995
  • Issued: 10/21/1997
  • Est. Priority Date: 02/24/1995
  • Status: Expired due to Fees
First Claim
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1. An echo canceling loudspeaker telephone comprising:

  • a loudspeaker for producing a sound pressure wave in response to an input signal which is applied to an audio input thereof, said sound pressure wave including a desired linear component which is a linear function of said input signal, and an undesired non-linear component which is a non-linear function of said input signal, said sound pressure wave being transmitted along an acoustic path;

    a microphone positioned in said acoustic path for converting said sound pressure wave into an output signal;

    an echo filter responsive to said input signal and which generates an estimated echo signal, said echo filter comprising a loudspeaker model which generates an estimate of said sound pressure wave including an estimate of said linear component and an estimate of said non-linear component, and an acoustic path model which generates an estimate of said acoustic path from said loudspeaker to said microphone;

    a subtractor for subtracting said estimated echo signal from said output signal thereby reducing an echo portion of said output signal; and

    an echo filter modifier responsive to said output signal said input signal and said estimated echo signal which determines a residual echo portion of said output signal remaining after subtracting said estimated echo signal from said output signal, and which modifies estimates of distortions due to said loudspeaker and said acoustic path in response to said residual echo portion to further reduce said echo portion of said output signal;

    wherein said loudspeaker model and said acoustic path model are connected in series.

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