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Echo cancellation methods and apparatus for voice processing systems

  • US 5,164,989 A
  • Filed: 12/11/1990
  • Issued: 11/17/1992
  • Est. Priority Date: 12/11/1990
  • Status: Expired due to Term
First Claim
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1. A voice processing system which applies an outgoing signal to a telephone connection and which receives and responds to an incoming signal from said telephone connection comprising:

  • echo modelling circuitry for applying a predetermined test signal to said telephone connection, said predetermined test signal, having the property that when said test signal is convolved with a time-inverse of said test signal a function that is approximately equal to an impulse is produced, said echo modelling circuitry analyzing the incoming signal subsequent to application of said test signal in order to determine how said test signal must be modified in accordance with an approximate impulse response that is calculated by said echo modelling circuitry so that when said test signal is combined with said incoming signal any echoes of said test signal present in said incoming signal are substantially eliminated, said echo modelling circuitry modifying said outgoing signal in accordance with said approximate impulse response to produce a modified version of said outgoing signal and subsequently combining said modified version of said outgoing signal with said incoming signal to substantially eliminate any echo of said test signal in said incoming signal.

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