Robust downlink speech and noise detector

• US 8,554,557 B2
• Filed: 11/14/2012
• Issued: 10/08/2013
• Est. Priority Date: 04/30/2008
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: QNX Software Systems Limited (Canada) (Blackberry Limited)
• Inventors: Hetherington, Phillip Alan
• Primary Examiner(s): ALBERTALLI, BRIAN LOUIS
• Application Number:
  US13/676,856
• Publication Number:
  US 20130073285A1
• Time in Patent Office: 328 Days
• Field of Search: None
• US Class Current: 704/233
• CPC Class Codes: G10L 25/78 Detection of presence or absence of voice signals switching of direction of transmission by voice frequency in two-way loud-speaking telephone systems H04M9/10
• CPC Class Codes: G10L 25/84 for discriminating voice from noise

Abstract

A voice activity detection process is robust to a low and high signal-to-noise ratio speech and signal loss. A process divides an aural signal into one or more bands. Signal magnitudes of frequency components and the respective noise components are estimated. A noise adaptation rate modifies estimates of noise components based on differences between the signal to the estimated noise and signal variability.

Claims

1. A noise estimation process, comprising:

estimating a signal magnitude of an aural signal;

estimating a noise magnitude of the aural signal;

setting a base adaptation rate based on a difference between the signal magnitude and the noise magnitude;

generating, by a programmed processor, a noise adaptation rate by modifying the base adaptation rate by an amount that varies based on one or more factors associated with the aural signal; and

modifying the estimated noise magnitude of the aural signal by the programmed processor based on the noise adaptation rate.

2. The noise estimation process of claim 1, further comprising dividing the aural signal into multiple frequency bands.

3. The noise estimation process of claim 2, where the steps of estimating the signal magnitude, estimating the noise magnitude, setting the base adaptation rate, generating the noise adaptation rate, and modifying the estimated noise magnitude are performed separately for each of the multiple frequency bands.

4. The noise estimation process of claim 2, where the multiple frequency bands comprise a low frequency band below a first cutoff frequency and a high frequency band above a second cutoff frequency.

5. The noise estimation process of claim 4, where the second cutoff frequency is higher than the first cutoff frequency.

6. The noise estimation process of claim 1, further comprising implementing voice and noise activity detection through power spectra following a Fast Fourier Transform (FFT) or through multiple filter banks.

7. The noise estimation process of claim 1, where the step of setting the base adaptation rate comprises setting a rise adaptation rate as the base adaptation rate when the difference between the signal magnitude and the noise magnitude indicates that a signal-to-noise ratio is above zero, and setting a fall adaptation rate, different than the rise adaptation rate, as the base adaptation rate when the difference between the signal magnitude and the noise magnitude indicates that the signal-to-noise ratio is below zero.

8. The noise estimation process of claim 1, where the one or more factors used to modify the base adaptation rate comprise a distance factor that indicates how different the signal magnitude is from the noise magnitude, and where the distance factor contributes an adaptation rate modification according to an inverse function of a signal-to-noise ratio.

9. The noise estimation process of claim 1, where the one or more factors used to modify the base adaptation rate comprise a variability factor that indicates a signal level variance present in the aural signal.

10. The noise estimation process of claim 1, where the one or more factors used to modify the base adaptation rate comprise a poor signal factor that compares the signal magnitude of the aural signal to a predetermined threshold, and where the poor signal factor contributes an adaptation rate reduction when the signal magnitude is below the predetermined threshold.

11. The noise estimation process of claim 1, further comprising identifying a voiced signal based on the noise adaptation rate.

12. The noise estimation process of claim 1, where the base adaptation rate is set for a first frame, and where the noise adaptation rate is generated for the first frame as a modified version of the base adaptation rate.

13. The noise estimation process of claim 1, where the noise adaptation rate is a multiplicative product of the base adaptation rate and the one or more factors.

14. The noise estimation process of claim 9, where the variability factor contributes an adaptation rate modification according to an inverse function of a signal variability measurement.

15. A noise estimation system, comprising:

one or more magnitude estimators configured to estimate a signal magnitude of an aural signal and a noise magnitude of the aural signal; and

a noise decision controller that comprises a programmed processor configured to;

set a base adaptation rate based on a difference between the signal magnitude and the noise magnitude;

generate a noise adaptation rate by modifying the base adaptation rate by an amount that varies based on one or more factors associated with the aural signal; and

modify the estimated noise magnitude of the aural signal based on the noise adaptation rate.

16. The noise estimation system of claim 15, further comprising a filter configured to divide the aural signal into multiple frequency bands, where the programmed processor is configured to estimate the signal magnitude, estimate the noise magnitude, set the base adaptation rate, generate the noise adaptation rate, and modify the estimated noise magnitude separately for each of the multiple frequency bands.

17. The noise estimation system of claim 15, where the programmed processor is configured to set the base adaptation rate by setting a rise adaptation rate as the base adaptation rate when the difference between the signal magnitude and the noise magnitude indicates that a signal-to-noise ratio is above zero, and by setting a fall adaptation rate, different than the rise adaptation rate, as the base adaptation rate when the difference between the signal magnitude and the noise magnitude indicates that the signal-to-noise ratio is below zero.

18. The noise estimation system of claim 15, where the one or more factors used to modify the base adaptation rate comprise a distance factor that indicates how different the signal magnitude is from the noise magnitude, and where the distance factor contributes an adaptation rate modification according to an inverse function of a signal-to-noise ratio.

19. The noise estimation system of claim 15, where the one or more factors used to modify the base adaptation rate comprise a variability factor that indicates a signal level variance present in the aural signal, and where the variability factor contributes an adaptation rate modification according to an inverse function of a signal variability measurement.

20. The noise estimation system of claim 15, where the one or more factors used to modify the base adaptation rate comprise a poor signal factor that compares the signal magnitude of the aural signal to a predetermined threshold, and where the poor signal factor contributes an adaptation rate reduction when the signal magnitude is below the predetermined threshold.

21. A non-transitory computer-readable medium with instructions stored thereon, where the instructions are executable by a processor to cause the processor to perform the steps of:

estimating a signal magnitude of an aural signal;

estimating a noise magnitude of the aural signal;

setting a base adaptation rate based on a difference between the signal magnitude and the noise magnitude;

generating a noise adaptation rate by modifying the base adaptation rate by an amount that varies based on one or more factors associated with the aural signal; and

modifying the estimated noise magnitude of the aural signal based on the noise adaptation rate.

22. The non-transitory computer-readable medium of claim 21, where the instructions executable by the processor to cause the processor to set the base adaptation rate comprise instructions executable by the processor to cause the processor to perform the steps of:

setting a rise adaptation rate as the base adaptation rate when the difference between the signal magnitude and the noise magnitude indicates that a signal-to-noise ratio is above zero; and

setting a fall adaptation rate, different than the rise adaptation rate, as the base adaptation rate when the difference between the signal magnitude and the noise magnitude indicates that the signal-to-noise ratio is below zero.

23. The non-transitory computer-readable medium of claim 21, where the one or more factors used to modify the base adaptation rate comprise a distance factor that indicates how different the signal magnitude is from the noise magnitude, and where the distance factor contributes an adaptation rate modification according to an inverse function of a signal-to-noise ratio.