Reverberation estimation and suppression system

• US 20060115095A1
• Filed: 12/01/2004
• Published: 06/01/2006
• Est. Priority Date: 12/01/2004
• Status: Active Grant

• Current Assignee: Blackberry Limited
• Original Assignee: Harman Becker Automotive Systems Wavemakers Inc (Blackberry Limited)
• Inventors: Hetherington, Phillip, Giesbrecht, David
• Granted Patent: US 8,284,947 B2
• Time in Patent Office: Days
• US Class Current: 381/66
• CPC Class Codes: H04M 9/08 Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic

Abstract

A signal processing system detects reverberation. The system may suppress the reverberation and improve signal quality. The system analyzes frequency bands of an input signal to determine whether reverberation characteristics are present. When reverberation is detected, the system may attenuate the reverberant frequency band to reduce or eliminate the reverberation.

Claims

1. A reverberation suppression system comprising:

signal analysis logic operative to identify a first reverberant characteristic in a first frequency band of a signal; and

attenuation logic responsive to the signal analysis logic and operable to attenuate the signal in the first frequency band.

2. The system of claim 1, where the first reverberant characteristic is an approximately linear decay rate in the first frequency band.

3. The system of claim 1, where the first reverberant characteristic is a decay rate in the first frequency band that approximately meets a first reverberation decay rate threshold.

4. The system of claim 3, where the first reverberation decay threshold is an enclosed space reverberation decay rate threshold.

5. The system of claim 3, where the first reverberation decay threshold is a vehicle interior reverberation decay rate threshold.

6. The system of claim 2, where the first reverberant characteristic is an approximately linear decay in dB over Time in the first frequency band.

7. The system of claim 1, where:

the signal analysis logic is further operable to identify a second reverberant characteristic in a second frequency band; and

the attenuation logic is also operable to responsively attenuate the signal in the second frequency band.

8. The system of claim 3, where:

the signal analysis logic is further operable to identify, in a second frequency band, a second reverberant characteristic comprising a second decay rate that approximately meets a second reverberation decay rate threshold; and

the attenuation logic is also operable to responsively attenuate the signal in the second frequency band.

9. The system of claim 8, where the first reverberation decay rate threshold and the second reverberation decay rate threshold are frequency band thresholds.

10. The system of claim 1, further comprising signal-to-noise ratio logic, where the analysis logic identifies the reverberant characteristic when the signal-to-noise ratio logic determines a positive signal-to-noise ratio.

11. The system of claim 1, further comprising adaptive filter logic operable to provide an estimate of an expected reverberation decay rate in the first frequency band.

12. A reverberation analysis system comprising:

a signal input;

signal analysis logic coupled to the signal input and operable to estimate a first decay rate for signal content of a first frequency band;

comparison logic coupled to the signal analysis logic and operable to compare the first decay rate to a first reverberation decay rate threshold; and

a signal output coupled to the comparison logic.

13. The system of claim 12, where:

the signal analysis logic is further operable to estimate a second decay rate for signal content of a second frequency band; and

the comparison logic is further operable to compare the second decay rate to a second reverberation decay rate threshold.

14. The system of claim 13, where the first and second frequency bands comprise Bark frequency bands.

15. The system of claim 13, where the first and second frequency bands comprise Mel frequency bands.

16. The system of claim 12, where the signal input couples a speech signal to the signal analysis logic.

17. The system of claim 12, where the signal analysis logic is operable to fit a line to signal decay over time in the first frequency band to estimate the first decay rate.

18. A method for suppressing reverberation, comprising:

determining a division of the signal into frequency bands;

determining a signal decay rate in at least one of the frequency bands;

identifying a reverberant frequency band based on the signal decay rate; and

attenuating the signal in the reverberant frequency band.

19. The method of claim 18, where identifying comprises:

determining whether the signal decay rate approximately meets a reverberation decay rate threshold.

20. The method of claim 18, where determining comprises:

determining the signal decay rate in each of the frequency bands;

determining whether each frequency band is a reverberant frequency band based on its signal decay rate; and

attenuating each reverberant frequency band.

21. The method of claim 18, where identifying comprises:

determining whether the signal decay rate is linear.

22. The method of claim 21, where identifying further comprises:

determining whether rate signal decay rate approximately meets a reverberation decay rate threshold.

23. The method of claim 19, where the reverberation decay rate threshold is an enclosed space reverberation decay rate threshold.

24. The method of claim 19, where the first reverberation decay threshold is a vehicle interior reverberation decay rate threshold.

25. A product comprising:

a machine readable medium; and

machine readable instructions embodied on the machine readable medium that;

determine a signal decay rate in a frequency band of an input signal;

identify a reverberant frequency band based on the signal decay rate; and

attenuate the signal in the reverberant frequency band.

26. The product of claim 25, where the instruction that determine the signal decay rate comprise instructions that:

fit a line to signal decay over time in the frequency band.

27. The product of claim 25, where the input signal is a speech signal.

28. The product of claim 25, further comprising instructions that:

determine a division of the input signal into Bark frequency bands.

29. The product of claim 25, further comprising instructions that:

determine a divisions fo the input signal into Mel frequency bands.

30. The product of claim 25, where the instructions that identify the reverberant frequency band comprise instructions that:

compare the signal decay rate to an office space reverberation decay rate threshold.

31. The product of claim 25, where the instructions that identify the reverberant frequency band comprise instructions that:

compare the signal decay rate to a vehicle interior reverberation decay rate threshold.

32. The product of claim 25, where the instructions that identify the reverberant frequency band comprise instructions that:

compare the signal decay rate to a mobile phone speakerphone reverberation decay rate threshold.

33. The product of claim 25, where the determination instructions, identification instructions, and attenuation instructions are responsive to detecting speech in the input signal.

34. The product of claim 25, where the determination instructions, identification instructions, and attenuation instructions are responsive to SNR in the input signal being above an SNR threshold.

35. The product of claim 25, where the instructions that attenuate the signal comprises instructions that attenuate multiple reverberant frequency bands.