Patent ID: 6757384
Filing Date: 2004-06-29
Classification: H04M

Abstract:
An echo cancellation method for use between at least two ends of a communication path having at least one audible sound sent from a first station at a first end of a communication path to a user at a second end of said communication path comprising the steps of:receiving said audible sound from said first station at a first input of an echo canceller; receiving an echo of said audible sound from a mismatch located between said echo canceller and said second end of said communication path; adapting a first set of coefficients of a digital filter to reduce a magnitude of said echo of said audible sound; storing said first set of coefficients; detecting a first double talk condition of a user speaking at the second end of said communication path at the same time that the audible sound is being received, said first double talk condition based on a comparison of the magnitude of said audible sound and the magnitude of a return signal comprising said echo and user speech from the second end of the communication path; detecting a second double talk condition of a user speaking at the second end of said communication path at the same time that the audible sound is being received, the second double talk condition based on a comparison of an echo cancelled signal having a first time constant and the echo cancelled signal having a second time constant longer than said first time constant, adapting another set of coefficients of said filter to reduce a magnitude of said audible sound echo if neither of said first and second double talk conditions are detected; and in response to the detecting of one of said first and second double talk conditions, stopping any adapting of any set of coefficients of said filter and substituting one of a first and second set of coefficients to operate said filter to reduce the echo of said audible sound, said first and second sets of coefficients corresponding to said first and second double talk conditions, respectively.