Full-duplex speakerphone circuit including a supplementary echo suppressor

• US 6,282,176 B1
• Filed: 03/20/1998
• Issued: 08/28/2001
• Est. Priority Date: 03/20/1998
• Status: Expired due to Term

• Current Assignee: Crystal Semiconductor Corporation (Cirrus Logic Incorporated)
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Hemkumar, Nariankadu D.
• Primary Examiner(s): Ton, Dang
• Assistant Examiner(s): Sam, Phirin
• Application Number:
  US09/045,736
• Time in Patent Office: 1,257 Days
• Field of Search: 370/276, 370/286, 370/287, 370/288, 370/289, 370/290, 370/291, 370/296, 370/297, 379/24, 379/400, 379/406, 379/407, 379/409, 379/410, 379/444, 379/78, 379/86, 379/88.07, 379/402, 379/403, 379/411, 379/420, 379/421, 379/422, 379/432
• US Class Current: 370/276
• CPC Class Codes: H04B 3/23 using a replica of transmitted signal in the time domain, e.g. echo cancellers
• CPC Class Codes: H04M 9/082 using echo cancellers echo cancellers per se H04B3/23

Abstract

A supplemental echo suppressor controls the attenuators in a transmit path and receive path to selectively set the attenuations based on the signal received from the far-end and the signal transmitted from the near-end. The attenuation levels are set to allow full-duplex communication. If both ends supply speech signals simultaneously, the attenuation is reduced, increasing the clarity of signals at both ends. Attenuation levels are also set when both ends are idle. If, however, the far-end user is talking and the near-end user is silent, and the echo at the near-end is low, then the attenuation is set high. Signal parameters are generated and monitored to control echo suppression. Suppression attenuation decisions are determined on the basis of normalized power estimates that are normalized to a background power estimate that is indicative of background noise. The power and noise parameters are used to determine engagement and disengagement of the suppressors. A slow noise signal is used as a control parameter for controlling suppression. The slow noise is a secondary, lower variance background power estimate that is derived from a background power estimate. The background power estimate, in turn, is derived from a power estimate of an input signal. An Echo Return-Loss Enhancement (ERLE) expectation value is used as a control parameter to discriminate between speech signals and echo signals which, in turn, is used to make suppression gain decisions.

Claims

1. A full-duplex communication circuit comprising:

a first signal path for carrying a first signal from a first-end input terminal at a first-end to a second-end output terminal at a second-end;

a second signal path for carrying a second signal from a second-end input terminal to a first-end output terminal;

a first signal path adaptive filter coupled to the first signal path and coupled to the second signal path for accessing the second signal, determining a compensation signal from the second signal, and compensating the first signal using the compensation signal to form a compensated first signal; and

a first signal path variable gain supplemental echo suppressor coupled between the second-end and the first-end, including;

a first signal path controllable attenuator coupled to the first signal path;

a first signal path power estimator coupled to the first signal path to receive the first signal and determine a power level of the first signal and coupled to the first signal path to receive the compensated first signal and determine a power level of the compensated first signal;

a first signal path noise estimator coupled to the first signal path power estimator to receive the power level of the compensated first signal and generate a first background power estimate;

a first signal path slow noise estimator coupled to the first signal path noise estimator to receive the first background power estimate and coupled to the first signal path power estimator to receive the power level of the first signal, the first signal path slow noise estimator to generate a lower variance first background power estimate;

a first signal path normalizer coupled to the first signal path power estimator and coupled to the first signal path slow noise estimator to normalize the first signal power level to the lower variance first background power estimate to determine a normalized first power level; and

a first signal path suppression controller coupled to the first signal path controllable attenuator and coupled to the first signal path normalizer, the first signal path suppression controller controlling the first signal path controllable attenuator as a function of the normalized first power level.

2. A circuit according to claim 1, further comprising:

an Echo Return-Loss Enhancement (ERLE) calculator coupled to the first signal path, the ERLE designating an amount of echo signal attenuation supplied by the first signal path adaptive filter;

the first signal path suppression controller controlling the first signal path controllable attenuator as a function of the ERLE.

3. A circuit according to claim 2, wherein:

the first signal path suppression controller controls the first signal path controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized first power level and the ERLE.

4. A circuit according to claim 1, further comprising:

a first-end speech detector coupled to the first signal path;

a second-end speech detector coupled to the second signal path; and

a double-talk detector coupled to the first signal path, wherein;

the first signal path suppression controller controls the first signal path controllable attenuator in a dual mode for the first signal path including a default_on mode and a default_off mode, in the default_on mode the first signal path suppression controller disengaging on an occurrence of first-end speech or double-talk, and in the default_off mode the first signal path suppression controller engaging when only second-end speech is occurring.

5. A circuit according to claim 1, wherein:

the first signal path suppression controller controls the first signal path controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized first power level.

6. A circuit according to claim 1, wherein:

the first signal path normalizer is coupled to the first signal path power estimator and coupled to the first signal path slow noise estimator to normalize the compensated first signal power level to the lower variance first background power estimate to determine a normalized compensated first power level.

7. A circuit according to claim 1, further comprising:

a second signal path adaptive filter coupled to the second signal path and coupled to the first signal path for accessing the first signal, determining a compensation signal from the first signal, and compensating the second signal using the compensation signal to form an compensated second signal; and

a second signal path variable gain echo suppressor further including;

a second signal path controllable attenuator coupled to the second signal path;

a second signal path power estimator coupled to the second signal path to receive the second signal and determine a power level of the second signal and coupled to the second signal path to receive the compensated second signal and determine a power level of the compensated second signal;

a second signal path noise estimator coupled to the second signal path power estimator to receive the power level of the compensated second signal and generate a second background power estimate;

a second signal path slow noise estimator coupled to the noise estimator to receive the second background power estimate and coupled to the second signal path power estimator to receive the power level of the second signal, the second signal path slow noise estimator to generate a lower variance second background power estimate;

a second signal path normalizer coupled to the second signal path power estimator and coupled to the second signal path slow noise estimator to normalize the second signal power level and the compensated second signal power level to the lower variance second background power estimate to determine a normalized second power level and a normalized compensated second power level, respectively; and

a second signal path suppression controller coupled to the second signal path controllable attenuator and coupled to the second signal path normalizer, the second signal path suppression controller controlling the controllable attenuator as a function of the normalized second power level.

8. A circuit according to claim 7, further comprising:

an Echo Return-Loss Enhancement (ERLE) calculator coupled to the second signal path, the ERLE designating an amount of echo signal attenuation supplied by the second signal path adaptive filter;

the second signal path suppression controller controlling the controllable attenuator as a function of the ERLE.

9. A circuit according to claim 8, wherein:

the second signal path suppression controller controls the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized second power level and the ERLE.

10. A circuit according to claim 7, further comprising:

a first-end speech detector coupled to the first signal path;

a second-end speech detector coupled to the second signal path; and

a second signal path double-talk detector coupled to the first signal path, wherein;

the second signal path suppression controller controls the controllable attenuator in a default_on mode for the second signal path, in the default_on mode the suppression controller disengaging on an occurrence of second-end speech or double-talk.

11. A circuit according to claim 7, wherein:

the second signal path normalizer is coupled to the second signal path power estimator and coupled to the second signal path slow noise estimator to normalize the compensated second signal power level to the lower variance second background power estimate to determine a normalized compensated second power level.

12. A circuit according to claim 7, wherein:

the second signal path suppression controller controls the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized second power level.

13. A full-duplex communication circuit comprising:

first signal path for carrying a first signal from a first-end input terminal at a first-end to a second-end output terminal at a second-end;

a second signal path for carrying a second signal from a second-end input terminal to a first-end output terminal;

an echo canceller coupled to the second signal path and coupled to the first signal path for accessing the first signal, determining a compensation signal from the first signal, and compensating the second signal using the compensation signal to form a compensated second signal; and

a variable gain echo suppressor coupled between the second-end and the first-end, and including;

a controllable attenuator coupled to the second signal path;

a power estimator coupled to the second signal path to receive the second signal and determine a power level of the second signal and coupled to the second signal path to receive the compensated second signal and determine a power level of the compensated second signal;

a noise estimator coupled to the power estimator to receive the power level of the compensated second signal and generate a second background power estimate;

a slow noise estimator coupled to the noise estimator to receive the second background power estimate and coupled to the power estimator to receive the power level of the second signal, the slow noise estimator to generate a lower variance second background power estimate;

a normalizer coupled to the power estimator and coupled to the slow noise estimator to normalize the second signal power level to the lower variance second background power estimate to determine a normalized second power level; and

a suppression controller coupled to the controllable attenuator and coupled to the normalizer, the suppression controller controlling the controllable attenuator as a function of the normalized second power level.

14. A circuit according to claim 13, further comprising:

an Echo Return-Loss Enhancement (ERLE) calculator coupled to the second signal path, the ERLE designating an amount of echo signal attenuation supplied by the echo canceller;

the suppression controller controlling the controllable attenuator as a function of the ERLE.

15. A circuit according to claim 14, wherein:

the suppression controller controls the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized second power level and the ERLE.

16. A circuit according to claim 14, further comprising:

a first-end speech detector coupled to the first signal path;

a second-end speech detector coupled to the second signal path; and

a double-talk detector coupled to the first signal path, wherein;

the suppression controller controls the controllable attenuator in a default_on mode for the second signal path, in the default_on mode the suppression controller disengaging on an occurrence of first-end speech or double-talk.

17. A circuit according to claim 14, wherein:

the suppression controller controls the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized second power level.

18. A circuit according to claim 13, wherein:

the second signal path normalizer is coupled to the second signal path power estimator and coupled to the second signal path slow noise estimator to normalize the compensated second signal power level to the lower variance second background power estimate to determine a normalized compensated second power level.

19. A full-duplex communication circuit comprising:

a first signal path for carrying a first signal from a first-end input terminal at a first-end to a second-end output terminal at a second-end;

a first-end speech detector coupled to the first signal path;

a double-talk detector coupled to the first signal path;

a second signal path for carrying a second signal from a second-end input terminal to a first-end output terminal;

a second-end speech detector coupled to the second signal path;

a variable gain echo suppressor coupled between the second-end and the first-end, and including;

a controllable attenuator coupled to the first signal path;

a signal path power estimator coupled to the first signal path to receive the first signal and determine a power level of the first signal and coupled to the first signal path to receive a compensated first signal and determine a power level of the compensated first signal;

a signal path noise estimator coupled to the signal path power estimator to receive the power level of the compensated first signal and generate a background power estimate;

a signal path slow noise estimator coupled to the signal path noise estimator to receive the background power estimate and coupled to the signal path power estimator to receive the power level of the compensated first signal, the signal path slow noise estimator to generate a lower variance background power estimate;

a normalizer coupled to the signal path power estimator and coupled to the signal path slow noise estimator to normalize the power level to the lower variance background power estimate to determine a normalized power level; and

a suppression controller coupled to the controllable attenuator and coupled to the normalizer.

20. A circuit according to claim 19, wherein:

the suppression controller controls the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized power level.

21. A circuit according to claim 19, further comprising:

an adaptive filter coupled to the first signal path and coupled to the second signal path for accessing the second signal, determining a compensation signal from the second signal, and compensating the first signal using the compensation signal to form the compensated first signal;

an Echo Return-Loss Enhancement (ERLE) calculator coupled to the first signal path, the ERLE designating an amount of echo signal attenuation supplied by the adaptive filter; and

the suppression controller controlling the controllable attenuator as a function of the ERLE.

22. A full-duplex communication circuit comprising:

a first signal path for carrying a first signal from a first-end input terminal at a first-end to a second-end output terminal at a second-end;

a first-end speech detector coupled to the first signal path;

a double-talk detector coupled to the first signal path;

a second signal path for carrying a second signal from a second-end input terminal to a first-end output terminal;

a variable gain echo suppressor coupled between the second-end and the first-end, and including;

a controllable attenuator coupled to the second signal path;

a signal path power estimator coupled to the first signal path to receive the first signal and determine a power level of the first signal and coupled to the first signal path to receive a compensated first signal and determine a power level of the compensated first signal;

a signal path noise estimator coupled to the signal path power estimator to receive the power level of the compensated first signal and generate a background power estimate;

a signal path slow noise estimator coupled to the signal path noise estimator to receive the background power estimate and coupled to the signal path power estimator to receive the power level of the compensated first signal, the signal path slow noise estimator to generate a lower variance background power estimate;

a normalizer coupled to the signal path power estimator and coupled to the signal path slow noise estimator to normalize the power level to the lower variance background power estimate to determine a normalized power level; and

a suppression controller coupled to the controllable attenuator and coupled to the normalizer.

23. A circuit according to claim 22, wherein:

the suppression controller controls the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized power level.

24. A circuit according to claim 22, further comprising:

an adaptive filter coupled to the first signal path and coupled to the second signal path for accessing the second signal, determining a compensation signal from the second signal, and compensating the first signal using the compensation signal to form the compensated first signal;

an Echo Return-Loss Enhancement (ERLE) calculator coupled to the second signal path, the ERLE designating an amount of echo signal attenuation supplied by the adaptive filter; and

the suppression controller controlling the controllable attenuator as a function of the ERLE.

25. A full-duplex communication circuit comprising:

a transmit signal path for carrying a transmit signal from a near-end input terminal at a near-end to a far-end output terminal at a far-end;

a receive signal path for carrying a receive signal from a far-end input terminal to a near-end output terminal;

an acoustic echo canceller coupled to the transmit signal path and coupled to the receive signal path for accessing the receive signal, determining an echo canceling signal from the receive signal, and echo canceling the transmit signal using the echo canceling signal to form an echo-canceled transmit signal; and

a variable gain echo suppressor coupled between the far-end and the near-end, including;

a controllable attenuator coupled to the transmit signal path,

a power estimator coupled to the transmit signal path to receive the transmit signal and determine a power level of the transmit signal and coupled to the transmit signal path to receive the echo-canceled transmit signal and determine a transmit power level of the echo-canceled transmit signal;

a noise estimator coupled to the power estimator to receive the power level of the echo-canceled transmit signal and generate a transmit background power estimate;

a slow noise estimator coupled to the noise estimator to receive the transmit background power estimate and coupled to the power estimator to receive the power level of the transmit signal, the slow noise estimator to generate a lower variance transmit background power estimate;

a normalizer coupled to the power estimator and coupled to the slow noise estimator to normalize the transmit signal power level to the lower variance transmit background power estimate to determine a normalized transmit power level; and

a suppression controller coupled to the controllable attenuator and coupled to the normalizer, the suppression controller controlling the controllable attenuator as a function of the normalized transmit power level.

26. A circuit according to claim 25, wherein:

the normalizer is coupled to the power estimator and coupled to the slow noise estimator to normalize the echo-canceled transmit signal power level to the lower variance transmit background power estimate to determine a normalized echo-canceled transmit power level.

27. A circuit according to claim 25, further comprising:

an Echo Return-Loss Enhancement (ERLE) calculator coupled to the transmit signal path, the ERLE designating an amount of echo signal attenuation supplied by the acoustic echo canceller;

the suppression controller controlling the controllable attenuator as a function of the ERLE.

28. A circuit according to claim 27, wherein:

the suppression controller controls the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized transmit power level and the ERLE.

29. A circuit according to claim 25, further comprising:

a near-end speech detector coupled to the transmit signal path,

a far-end speech detector coupled to the receive signal path; and

a double-talk detector coupled to the transmit signal path, wherein;

the suppression controller controls the controllable attenuator in a dual mode for the transmit signal path including a default_on mode and a default_off mode, in the default_on mode the suppression controller disengaging on an occurrence of near-end speech or double-talk, and in the default_off mode the suppression controller engaging when only far-end speech is occurring.

30. A circuit according to claim 25, wherein:

the suppression controller controls the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized transmit power level.

31. A circuit according to claim 25, further comprising:

a network echo canceller coupled to the receive signal path and coupled to the transmit signal path for accessing the transmit signal, determining an echo canceling signal from the transmit signal, and echo canceling the receive signal using the echo canceling signal to form an echo-canceled receive signal; and

the variable gain echo suppressor further including;

a controllable attenuator coupled to the receive signal path;

a power estimator coupled to the receive signal path to receive the receive signal and determine a power level of the receive signal and coupled to the receive signal path to receive the echo-canceled receive signal and determine a power level of the echo-canceled receive signal;

a noise estimator coupled to the power estimator to receive the echo-canceled receive signal estimate and generate a receive background power estimate;

a slow noise estimator coupled to the noise estimator to receive the receive background power estimate and coupled to the power estimator to receive the power level of the receive signal, the slow noise estimator to generate a lower variance receive background power estimate;

a normalizer coupled to the power estimator and coupled to the slow noise estimator to normalize the receive signal power level to the lower variance receive background power estimate to determine a normalized receive power level; and

a suppression controller coupled to the controllable attenuator and coupled to the normalizer, the suppression controller controlling the controllable attenuator as a function of the normalized receive power level.

32. A circuit according to claim 31, further comprising:

an Echo Return-Loss Enhancement (ERLE) calculator coupled to the receive signal path, the ERLE designating an amount of echo signal attenuation supplied by the network echo canceller;

the suppression controller controlling the controllable attenuator as a function of the ERLE.

33. A circuit according to claim 32, wherein:

the suppression controller controls the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized receive power level and the ERLE.

34. A circuit according to claim 31, further comprising:

a near-end speech detector coupled to the transmit signal path;

a far-end speech detector coupled to the receive signal path; and

a double-talk detector coupled to the transmit signal path, wherein;

the suppression controller controls the controllable attenuator in a default_on mode for the receive signal path, in the default_on mode the suppression controller disengaging on an occurrence of far-end speech or double-talk.

35. A circuit according to claim 31, wherein:

the suppression controller controls the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized receive power level.

36. A full-duplex communication circuit comprising:

A transmit signal path for carrying a transmit signal from a near-end input terminal at a near-end to a far-end output terminal at a far-end;

a receive signal path for carrying a receive signal from a far-end input terminal to a near-end output terminal;

a network echo canceller coupled to the receive signal path and coupled to the transmit signal path for accessing the transmit signal, determining an echo canceling signal from the transmit signal, and echo canceling the receive signal using the echo canceling signal to form an echo-canceled receive signal; and

a variable gain echo suppressor coupled between the far-end and the near-end, and including;

a controllable attenuator coupled to the receive signal path;

a power estimator coupled to the receive signal path to receive the receive signal and determine a power level of the receive signal and coupled to the receive signal path to receive the echo-canceled receive signal and determine a power level of the echo-canceled receive signal;

a noise estimator coupled to the power estimator to receive the power level of the echo-canceled receive signal and generate a receive background power estimate;

a slow noise estimator coupled to the noise estimator to receive the receive background power estimate and coupled to the power estimator to receive the power level of the receive signal, the slow noise estimator to generate a lower variance receive background power estimate;

a normalizer coupled to the power estimator and coupled to the slow noise estimator to normalize the receive signal power level to the lower variance receive background power estimate to determine a normalized receive power level; and

a suppression controller coupled to the controllable attenuator and coupled to the normalizer, the suppression controller controlling the controllable attenuator as a function of the normalized receive power level.

37. A circuit according to claim 36, wherein:

the normalizer is coupled to the power estimator and coupled to the slow noise estimator to normalize the echo-canceled receive signal power level to the lower variance receive background power estimate to determine a normalized echo-canceled receive power level.

38. A circuit according to claim 36, further comprising:

an Echo Return-Loss Enhancement (ERLE) calculator coupled to the receive signal path, the ERLE designating an amount of echo signal attenuation supplied by the network echo canceller;

the suppression controller controlling the controllable attenuator as a function of the ERLE.

39. A circuit according to claim 38, wherein:

the suppression controller controls the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized receive power level and the ERLE.

40. A circuit according to claim 38, further comprising:

a near-end speech detector coupled to the transmit signal path,

a far-end speech detector coupled to the receive signal path; and

a double-talk detector coupled to the transmit signal path, wherein;

the suppression controller controls the controllable attenuator in a default_on mode for the receive signal path in the default_on mode the suppression controller disengaging on an occurrence of near-end speech or double-talk.

41. A circuit according to claim 38, wherein:

the suppression controller controls the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized receive power level.

42. A full-duplex communication circuit comprising:

a transmit signal path for carrying transmit signals from a near-end input terminal at a near-end to a far-end output terminal at a far-end;

a near-end speech detector coupled to the transmit signal path;

a double-talk detector coupled to the transmit signal path;

a receive signal path for carrying receive signals from a far-end input terminal to a near-end output terminal;

a far-end speech detector coupled to the receive signal path;

a variable gain echo suppressor coupled between the far-end and the near-end, and including;

a controllable attenuator coupled to the transmit signal path;

a signal path power estimator coupled to the first signal path to receive a first signal and determine a power level of the first signal and coupled to the first signal path to receive a compensated first signal and determine a power level of the compensated first signal;

a signal path noise estimator coupled to the signal path power estimator to receive the power level of the compensated first signal and generate a background power estimate;

a signal path slow noise estimator coupled to the signal path noise estimator to receive the background power estimate and coupled to the signal path power estimator to receive the power level of the compensated first signal, the signal path slow noise estimator to generate a lower variance background power estimate;

a normalizer coupled to the signal path power estimator and coupled to the signal path slow noise estimator to normalize the power level to the lower variance background power estimate to determine a normalized power level; and

a suppression controller coupled to the controllable attenuator and coupled to the normalizer.

43. A circuit according to claim 42, wherein:

the suppression controller controls the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized power level.

44. A circuit according to claim 42, further comprising:

an Echo Return-Loss Enhancement (ERLE) calculator coupled to the transmit signal path, the ERLE designating an amount of echo signal attenuation supplied by the network echo canceller; and

the suppression controller controlling the controllable attenuator as a function of the ERLE.

45. A full-duplex communication circuit comprising:

a transmit signal path for carrying transmit signals from a near-end input terminal at a near-end to a far-end output terminal at a far-end;

a near-end speech detector coupled to the transmit signal path;

a double-talk detector coupled to the transmit signal path;

a receive signal path for carrying receive signals from a far-end input terminal to a near-end output terminal;

a variable gain echo suppressor coupled between the far-end and the near-end, and including;

a controllable attenuator coupled to the receive signal path;

a signal path power estimator coupled to the first signal path to receive a first signal and determine a power level of the first signal and coupled to the signal path to receive a compensated first signal and determine a power level of the compensated first signal;

a signal path noise estimator coupled to the signal path power estimator to receive the power level of the compensated first signal and generate a background power estimate;

a signal path slow noise estimator coupled to the signal path noise estimator to receive the background power estimate and coupled to the signal path power estimator to receive the power level of the compensated first signal, the signal path slow noise estimator to generate a lower variance background power estimate;

a normalizer coupled to the signal path power estimator and coupled to the signal path slow noise estimator to normalize the power level to the lower variance background power estimate to determine a normalized power level; and

a suppression controller coupled to the controllable attenuator and coupled to the normalizer.

46. A circuit according to claim 45, wherein:

the suppression controller controls the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized power level.

47. A circuit according to claim 45, further comprising:

an Echo Return-Loss Enhancement (ERLE) calculator coupled to the receive signal path, the ERLE designating an amount of echo signal attenuation supplied by the network echo canceller; and

the suppression controller controlling the controllable attenuator as a function of the ERLE.

48. A method of controlling a full-duplex communication circuit comprising:

accessing a receive signal from a receive signal path carrying receive signals from a far-end input terminal to a near-end output terminal;

accessing a transmit signal from a transmit signal path carrying transmit signals from a near-end input terminal to a far-end output terminal;

canceling an acoustic echo including;

determining an echo canceling signal from the receive signal; and

echo canceling the transmit signal using the echo canceling signal to form an echo-canceled transmit signal;

determining, by a signal path power estimator coupled to the transmit signal, a power level of the transmit signal;

determining, by the signal path power estimator, a transmit power level of the echo-canceled transmit signal;

generating, by a signal path noise estimator coupled to the signal path power estimator, a transmit background power estimate from the transmit power level of the echo-canceled transmit signal;

generating, by a signal path slow noise estimator coupled to the signal path noise estimator, a lower variance transmit background power estimate from the transmit background power estimate;

normalizing, by a normalizer coupled to the signal path power estimator, the transmit signal power level to the lower variance transmit background power estimate to determine a normalized transmit power level; and

controlling, by a suppression controller, a controllable attenuator as a function of the normalized transmit power level.

49. A method according to claim 48, further comprising:

normalizing, by the normalizer, the echo-canceled transmit signal power level to the lower variance transmit background power estimate to determine a normalized echo-canceled transmit power level.

50. A method according to claim 48, further comprising:

calculating, by an Echo Return-Loss Enhancement (ERLE) calculator, the ERLE designating an amount of echo signal attenuation supplied by canceling the acoustic echo; and

controlling, by the suppression controller, the controllable attenuator as a function of the ERLE.

51. A method according to claim 50, further comprising:

controlling, by the suppression controller, the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized transmit power level and the ERLE.

52. A method according to claim 48, further comprising:

detecting, by a near-end speech detector, near-end speech in the transmit signal path;

detecting, by a far-end speech detector, far-end speech in the receive signal path;

detecting, by a double-talk detector, double-talk in the receive signal path and the transmit signal path;

controlling, by the suppression controller, the controllable attenuator in a dual mode for the transmit signal path including a default_on mode and a default_off mode, in the default_on mode the suppression controller disengaging on an occurrence of near-end speech or double-talk, and in the default_off mode the suppression controller engaging when only far-end speech is occurring.

53. A method according to claim 48, further comprising:

controlling, by the suppression controller, the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized transmit power level.

54. A method of controlling a full-duplex communication circuit comprising:

accessing a receive signal from a receive signal path carrying receive signals from a far-end input terminal to a near-end output terminal;

accessing a transmit signal from a transmit signal path carrying transmit signals from a near-end input terminal to a far-end output terminal;

canceling a network echo including;

determining, by a network echo canceller, an echo canceling signal from the transmit signal; and

echo canceling, by the network echo canceller, the receive signal using the echo canceling signal to form an echo-canceled receive signal;

determining, by a power estimator, a power level of the transmit signal;

determining, by the power estimator, a receive power level of the echo-canceled receive signal;

generating, by a noise estimator, a receive background power estimate from the receive power level of the echo-canceled receive signal;

generating, by a slow noise estimator, a lower variance receive background power estimate from the receive background power estimate;

normalizing, by a normalizer, the receive signal power level to the lower variance receive background power estimate to determine a normalized receive power level; and

controlling, by a suppression controller, a controllable attenuator as a function of the normalized receive power level.

55. A method according to claim 54, further comprising:

normalizing, by the normalizer, the echo-canceled receive signal power level to the lower variance receive background power estimate to determine a normalized echo-canceled receive power level.

56. A method according to claim 54, further comprising:

calculating, by an Echo Return-Loss Enhancement (ERLE) calculator, the ERLE designating an amount of echo signal attenuation supplied by canceling the network echo; and

controlling, by the suppression controller, the controllable attenuator as a function of the ERLE.

57. A method according to claim 56, further comprising:

controlling, by the suppression controller, the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized receive power level and the ERLE.

58. A method according to claim 54, further comprising:

detecting, by a near-end speech detector, near-end speech in the transmit signal path;

detecting, by a far-end speech detector, far-end speech in the receive signal path;

detecting, by a double-talk detector, double-talk in the receive signal path and the transmit signal path;

controlling, by the suppression controller, the controllable attenuator in a default_on mode for the receive signal path, in the default_on mode the suppression controller disengaging on an occurrence of near-end speech or double-talk.

59. A method according to claim 54, further comprising:

controlling, by the suppression controller, the controllable attenuator by gradually engaging and disengaging a fixed attenuation as a function of the normalized receive power level.