Telephonic communications – Echo cancellation or suppression
Patent
1997-12-11
2000-04-11
Isen, Forester W.
Telephonic communications
Echo cancellation or suppression
379407, 379410, 381 66, H04M 908
Patent
active
060496061
ABSTRACT:
The invention provides an audio subsystem for use in a telephone terminal operable in handsfree mode and comprises a receive path including a receive transducer for generating audio signals from a received signal and a transmit path including a transmit transducer for converting audio signals to electrical signals for transmission to a far-end user. An acoustic echo canceller is communicatively coupled between the receive path and the transmit path and includes a subtractor circuit connected serially with the transmit transducer. The echo canceller is responsive to control signals for controlling the subtractor circuit. The subsystem comprises means for detecting a near-end talking condition including first circuit means for measuring the level of the total energy of the out-of-telephony-band components in the signal from the transmit transducer and circuit means for comparing the energy level represented by an output signal from the first measurement circuit to a first predetermined threshold. If the measured energy level exceeds the predetermined threshold, near-end talking activity is deemed to exist. There is also provided a second measurement circuit for measuring the level of the signal on the receive path and for comparing it to a second predetermined threshold whereby if the latter is exceeded, far-end talking activity is determined to exist. Thus, if both measured signals exceed their respective threshold, a double talk situation is deemed to exist.
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Ding Heping
Lau Frank
Isen Forester W.
Nortel Networks Corporation
Saint-Surin Jacques M.
Smith Dallas F.
Turpin Frank P.
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