Voice enhancement system and method

• US 5,471,527 A
• Filed: 12/02/1993
• Issued: 11/28/1995
• Est. Priority Date: 12/02/1993
• Status: Expired due to Term

• Current Assignee: Alcatel-Lucent USA, Inc. (Nokia Corporation)
• Original Assignee: DSC Communications Corp. (Nokia Corporation)
• Inventors: Pratt, Michael K., Oshidari, Thomas T., Lim, Pong C., Ho, Helena S.
• Primary Examiner(s): Hofsass, Jeffery A.
• Assistant Examiner(s): HUNTER, DANIEL S
• Application Number:
  US08/161,120
• Time in Patent Office: 726 Days
• Field of Search: 379/400, 379/340, 379/347, 379/395, 379/401, 379/406, 379/409, 379/410, 379/411, 379/414, 379/415-419, 381/98, 381/101, 381/102, 381/103
• US Class Current: 379/347
• CPC Class Codes: H03G 5/22 having semiconductor devices
• CPC Class Codes: H04M 3/002 Applications of echo suppressors or cancellers in telephonic connections in two-way loud-speaking telephone systems H04M9/08, echo suppressors or cancellers per se H04B3/20
• CPC Class Codes: H04M 3/40 Applications of speech amplifiers

Abstract

A telecommunications network (120) is provided with adaptive gain control (AGC) of the voice signals in network (120). Network (120) includes an input (12) for receiving a voice signal, an output (14) for receiving the voice signal, and a coupling between input (12) and output (14) including at least one switch (124) or (126). Network (120) also includes voice enhancer (10) including power averager (18) for measuring and determining the average power of an input signal. Voice enhancer (10) also includes bass band equalizer (16) to attenuate a predetermined portion of the input signal to provide an equalized input signal. From the average power of the input signal is determined a scaling factor from a gain/attenuation look-up table (28). Voice enhancer (10) also includes output scaler (30) coupled to output (14), output scaler (30) scales the equalized input signal with the scaling factor and provides the scaled signal to output (14). Voice enhancer (10) also includes bass to treble power comparator (20) for detecting tandem enhancement and voice-band data detector (22) which cause enhancer (10) to be disabled appropriately.

Claims

1. A method for providing voice enhancement in a telecommunications network, comprising the steps of:

determining the average power of an input voice-band signal;

determining a scaling factor in response to the average power of the input voice-band signal;

equalizing the input voice-band signal by attenuating a predetermined portion of the input voice-band signal;

scaling the equalized input voice-band signal with the scaling factor;

measuring the power of the input voice-band signal above and below a predetermined frequency;

comparing the power measurements to power measurements expected for a previously scaled signal; and

coupling the scaled voice-band signal to an output or decoupling the scaled voice-band signal from the output in response to the comparing step.

2. The method of claim 1 further comprising the steps of:

detecting voice-band data in the input signal; and

decoupling the scaled voice band signal from the output.

3. The method of claim 1 wherein said determining the average power, determining a scaling factor, equalizing, scaling, and coupling steps are performed in an echo canceller of a telecommunications network.

4. The method of claim 1 wherein the predetermined portion of the input voice band signal is above substantially 300 Hz.

5. The method of claim 1 wherein the predetermined portion of the input voice band signal is above substantially 400 Hz.

6. The method of claim 1 wherein said scaling the input signal step further comprises using the scaling factor for scaling the equalized input signal for a predetermined period of time.

7. The method of claim 1 further comprising the steps of:

dividing the input voice band signal into a plurality of frames, each frame representative of a period of time; and

scaling the equalized input signal with the scaling factor for a predetermined number of frames.

8. The method of claim 1 wherein said determining a scaling factor step further comprises the step of limiting the amount of change between consecutive scaling factors.

9. The method of claim 1 wherein said equalizing step further comprises filtering the input signal such that the power of the input signal above a predetermined frequency is attenuated.

10. The method of claim 1 wherein said determining the average power step further comprises low pass filtering a rectified input voice band signal.

11. The method of claim 1 further comprising the steps of:

dividing the input voice band signal into a plurality of frames, each frame representative of a period of time;

continuously performing said determining the average power, determining a scaling factor, equalizing, scaling, and coupling steps upon the expiration of a predetermined number of frames.

12. The method of claim 1 further comprising the steps of:

detecting periods of silence in the input voice band signal at the input; and

decoupling the scaled voice band signal from the output.

13. The method of claim 12 further comprising the step of attenuating the input voice band signal so that the noise level of the detected periods of silence is minimized.

14. A method for providing voice enhancement in a telecommunications network, comprising the steps of:

determining the average power of an input voice-band signal;

determining a scaling factor in response to the average power of the input voice-band signal;

equalizing the input voice-band signal by attenuating a predetermined portion of the input voice-band signal;

scaling the equalized input voice-band signal with the scaling factor;

measuring the power of the input voice-band signal above and below a predetermined frequency;

comparing the power measurements to power measurements expected for a previously scaled signal;

coupling the scaled voice-band signal to an output or decoupling the scaled voice-band signal from the output in response to said comparing step; and

detecting voice-band data in the input signal and decoupling the scaled voice-band signal from the output.

15. The method of claim 14 wherein said determining the average power, determining a scaling factor, equalizing, scaling, and coupling steps are performed in an echo canceller of a telecommunications network.

16. The method of claim 14 wherein the predetermined portion of the input voice band signal is above substantially 300 Hz.

17. The method of claim 14 further comprising the steps of:

dividing the input voice band signal into a plurality of frames, each frame representative of a period of time; and

scaling the equalized input signal with the scaling factor for a predetermined number of frames.

18. The method of claim 14 further comprising the steps of:

dividing the input voice band signal into a plurality of frames, each frame representative of a period of time;

continuously performing said determining the average power, determining a scaling factor, equalizing, scaling, and coupling steps upon the expiration of a predetermined number of frames.

19. The method of claim 14 further comprising the steps of:

detecting periods of silence in the input voice band signal at the input; and

decoupling the scaled voice band signal from the output.

20. The method of claim 19 further comprising the step of attenuating the input voice band signal so that the level of the detected periods of silence is minimized.

21. A system for providing enhancement to a voice-band signal in a telecommunications network, comprising:

a power averager for determining the average power of the voice-band signal;

an equalizer for attenuating a predetermined portion of the voice-band signal;

an output scaler for scaling the equalized voice-band signal with a scaling factor in response to the determined average power;

a tandem voice enhancement detector for detecting when the voice-band signal has been previously scaled, wherein the tandem voice enhancement detector

measures the power in the voice-band signal above and below a predetermined frequency,

compares the power measurements to power measurements expected for a previously scaled signal, and

prevents the equalizer and the output scaler from equailizing and scaling the voice-band signal in response to the comparison.

22. The system of claim 21 further comprising a voice-band data detector for detecting voice-band data in the voice band signal and preventing said output scaler from scaling the voice band signal.

23. The system of claim 21 wherein said power averager, equalizer, and output scaler are located in an echo canceller of a telecommunications network.

24. The system of claim 21 wherein the predetermined portion of the voice band signal attenuated by said equalizer is above substantially 300 Hz.

25. The system of claim 21 wherein the predetermined portion of the voice band signal attenuated by said equalizer is above substantially 400 Hz.

26. The system of claim 21 wherein said output scaler is operable to scale equalized voice band signals with a previously determined scaling factor for a predetermined period of time.

27. The system of claim 21 wherein said output scaler is further operable to divide the voice band signal into a plurality of frames, each frame representative of a period of time, and to scale the voice band signal for a predetermined number of frames.

28. The system of claim 21 wherein said output scaler is further operable to limit the amount of change between consecutive scaling factors.

29. The system of claim 21 wherein said equalizer comprises a digital filter operable to filter the voice band signal above a predetermined frequency.

30. The system of claim 21 wherein said power averager comprises a low pass filter.

31. The system of claim 21 further comprising a gain/attenuation look-up table for providing the scaling factor to be used by said output scaler in scaling the voice band signal.

32. The system of claim 21 further comprising a gain/attenuation look-up table for providing the scaling factor to be used by said output scaler in scaling the voice band signal, and wherein said gain/attenuation look-up table is organized such that low power voice band signals are assigned large scaling factors relative to high power voice band signals, the high power voice band signals being assigned low or negative scaling factors.

33. The system of claim 21 further comprising:

a transparent path for providing the input voice band signal directly to an output so that the input voice band signal avoids scaling; and

an attenuator coupled in said transparent path for variably attenuating low level input signals lacking voice band signals.

34. A system for providing enhancement to a voice-band signal in a telecommunications network, comprising:

an input for accepting the voice-band signal;

an output for receiving a signal; and

a coupling between said input and output including a voice enhancer, said voice enhancer comprising;

a power averager for determining the average power of the voice-band signal;

an equalizer for attenuating a predetermined portion of the voice-band signal;

an output scaler coupled to said output for scaling the equalized voice-band signal with a scaling factor in response to the determined average power and providing the scaled signal to said output; and

a tandem voice enhancement detector for detecting when the voice-band signal has been previously scaled, wherein the tandem voice enhancement detector

measures the power in the voice-band signal above and below a predetermined frequency,

compares the power measurements to power measurements expected for a previously scaled signal, and

decouples said output scaler from said output in response to said comparing step.

35. The system of claim 34 further comprising a voice-band data detector for detecting voice-band data in the voice band signal and for decoupling said output scaler from said output.