Robust noise estimation

• US 8,260,612 B2
• Filed: 12/09/2011
• Issued: 09/04/2012
• Est. Priority Date: 05/12/2006
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: QNX Software Systems Limited (Canada) (Blackberry Limited)
• Inventors: Hetherington, Phillip A.
• Primary Examiner(s): Smits, Talivaldis Ivars
• Assistant Examiner(s): ROBERTS, SHAUN A
• Application Number:
  US13/315,636
• Publication Number:
  US 20120078620A1
• Time in Patent Office: 270 Days
• Field of Search: 704/226, 704/228, 704/233, 381/94.3
• US Class Current: 704/226
• CPC Class Codes: G10L 21/0208 Noise filtering
• 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

An enhancement system improves the estimate of noise from a received signal. The system includes a spectrum monitor that divides a portion of the signal at more than one frequency resolution. Adaptation logic derives a noise adaptation factor of the received signal. A plurality of devices tracks the characteristics of an estimated noise in the received signal and modifies multiple noise adaptation rates. Weighting logic applies the modified noise adaptation rates derived from the signal divided at a first frequency resolution to the signal divided at a second frequency resolution.

Claims

1. A system operative to estimate noise in a signal, comprising:

a spectrum monitor to divide a portion of a frequency spectrum of the signal into a plurality of frequency bands, each frequency band containing one or more frequency bins;

one or more logical devices to track characteristics of a noise estimate for each of the frequency bands and to modify a plurality of noise estimate adaption rates, each corresponding to one of the plurality of frequency bands; and

a noise estimator to revise a noise estimate, for each of the frequency bins, responsive to the signal and to the noise estimate adaption rates of one or more frequency bands that contain the frequency bin.

2. The system of claim 1, further comprising a limiting logic operative to constrain the modification of the plurality of noise estimate adaption rates.

3. The system of claim 1, wherein the frequency bands are differentially spaced according to logarithmic, Mel, or Bark scaling.

4. The system of claim 1, wherein the plurality of frequency bands are overlapping.

5. The system of claim 1, further comprising weighting logic to apply the plurality of noise estimate adaption rates of the one or more frequency bands that contain the frequency bin to the noise estimate for the frequency bin according to weighting functions.

6. The system of claim 1, wherein an initial noise adaption rate for each of the plurality of noise adaption rates is pre-programmed or is derived from the portion of the frequency spectrum of the signal through logic.

7. The system of claim 1, wherein the one or more logical devices comprise noise-as-an-estimate-of-the-signal logic, temporal variability logic, time in transient logic, or peer pressure logic.

8. A system operative to estimate noise in a signal, comprising:

a spectrum monitor configured to divide the signal into a plurality of frequency bands, where each frequency band comprises one or more frequency bins;

a logical device configured to track noise characteristics of a frequency band of the plurality of frequency bands and to modify a noise estimate adaption rate associated with the frequency band; and

a noise estimator configured to revise a noise estimate, for a frequency bin of the frequency band, in response to the noise estimate adaption rate of the frequency band.

9. The system of claim 8 where the logical device comprises noise-as-an-estimate-of-the-signal logic configured to modify the noise estimate adaption rate based on a fit between an estimated noise and the signal.

10. The system of claim 8 where the logical device comprises temporal variability logic configured to modify the noise estimate adaption rate based on how much the signal fluctuates as the signal evolves over time.

11. The system of claim 8 where the logical device comprises time in transient logic configured to modify the noise estimate adaption rate based on a function correlated to an amount of time that a signal estimate is above an estimated noise level by a predetermined level.

12. The system of claim 8 where the logical device comprises peer pressure logic configured to modify the noise estimate adaption rate associated with the frequency band based on trends from other frequency bands.

13. The system of claim 8 where the logical device comprises circuitry operable to modify the noise estimate adaption rate.

14. The system of claim 8 where the logical device comprises a computer processor that executes instructions stored on a non-transitory computer-readable medium to modify the noise estimate adaption rate.

15. A method of estimating noise, comprising:

dividing a signal into a plurality of frequency bands, where each frequency band comprises one or more frequency bins;

tracking noise characteristics of a frequency band of the plurality of frequency bands;

modifying a noise estimate adaption rate associated with the frequency band; and

revising a noise estimate, for a frequency bin of the frequency band, in response to the noise estimate adaption rate of the frequency band.

16. The method of claim 15, where the step of modifying the noise estimate adaption rate comprises modifying the noise estimate adaption rate based on a fit between an estimated noise and the signal.

17. The method of claim 15, where the step of modifying the noise estimate adaption rate comprises modifying the noise estimate adaption rate based on how much the signal fluctuates as the signal evolves over time.

18. The method of claim 15, where the step of modifying the noise estimate adaption rate comprises modifying the noise estimate adaption rate based on a function correlated to an amount of time that a signal estimate is above an estimated noise level by a predetermined level.

19. The method of claim 15, where the step of modifying the noise estimate adaption rate comprises modifying the noise estimate adaption rate associated with the frequency band based on trends from other frequency bands.

20. The method of claim 15, where the step of modifying the noise estimate adaption rate comprises modifying the noise estimate adaption rate by a computer processor that executes instructions stored on a non-transitory computer-readable medium.