Echo cancellation method and apparatus

Details Echo cancellation method and apparatus Echo cancellation method and apparatus

2005-03-08

2005-03-08

Mei, Xu (Department: 2644)

Telephonic communications

Echo cancellation or suppression

Combined diverse function

C379S406060, C708S322000

Reexamination Certificate

active

06865270

ABSTRACT:
An echo cancellation invention which does away with the need for an accurate double-talk detector, while maintaining a higher adaptation gain for quicker convergence and also providing increased stability. It does this by operating two filter models of the acoustic path in parallel. One model is adapted continuously to find the most accurate model of the echo path, while the other is not. The echo canceller output is taken from the filter that is not adapted. A comparison of the residual error (echo) is done between the model being adapted and the model being listened to at regular intervals. When the model being adapted has less error (echo) than the model being listened to its filter coefficients are copied to the other model. If the model being adapted has greater error (echo) than the other model (caused by noise diverging the adaptation process) then the adapted model has its coefficients overwritten by the filter that is listened to. This process keeps error from accumulating in the adapted filter by removing divergence at regular intervals (improving overall convergence). Since the output is taken from the filter that is not adapted, higher adaptation gains may be used without fear of the user hearing any effects of adapting with a higher gain in the presence of noise.

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Kazuo Ochiai, Takashi Araseki and Takashi Ogihara, “Echo Canceler with Two Echo Path Models”IEEE Transactions on Communications, vol. Com-25, No. 6, Jun. 1977.
Hua Ye and Bo-Xiu Wu, “A New Double-Talk Detection Algorithm Based on the Orthogonality Theorem”,IEEE Transactions on Communications, vol. 39, No. 11, Nov. 1991.
Simon Haykin,Adaptive Filter Theory, 3rd Ed., 1996, pp. 432-439; 746-747, Prentice Hall.

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