Robust noise estimation

• US 7,844,453 B2
• Filed: 12/22/2006
• Issued: 11/30/2010
• Est. Priority Date: 05/12/2006
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: QNX Software Systems Company (Blackberry Limited)
• Inventors: Hetherington, Phillip A.
• Primary Examiner(s): Hudspeth; David R
• Assistant Examiner(s): ROBERTS, SHAUN A
• Application Number:
  US11/644,414
• Publication Number:
  US 20070265843A1
• Time in Patent Office: 1,439 Days
• Field of Search: 704/226, 704/228, 704/233, 381/94.3
• US Class Current: 704/228
• 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. An enhancement system operative to estimate noise from a received signal comprising:

a spectrum monitor operative to divide a portion of a received signal at more than one frequency resolution;

a global adaptation logic operative to derive a noise adaptation factor of the received signal;

a plurality of logical devices programmed to track characteristics of an estimated noise in the received signal and modify a plurality of noise adaptation rates of portions of the received signal divided at a first frequency resolution;

a weighting logic applied to one or more of the tracked characteristics of the estimated noise in the received signal, the weighting logic being operative to derive a value that when compared to a predetermined threshold indicates a presence of speech; and

a limiting logic operative to constrain the modified plurality of noise adaptation rates.

2. The system of claim 1 where the spectrum monitor is configured to divide the portion of the received signal into at least two frequency resolutions.

3. The system of claim 1 where some of the plurality of logical devices compensate for inexact changes to the modified plurality of noise adaptation rates.

4. The system of claim 1 where one of the plurality of logical devices comprises noise-as-an-estimate-of-the-signal logic.

5. The system of claim 1 where one of the plurality of logical devices comprises temporal variability logic.

6. The system of claim 1 where one of the plurality of logical devices comprises time in transient logic.

7. The system of claim 1 where one of the plurality of logical devices comprises peer pressure logic.

8. The system of claim 1 where one of the plurality of logical devices comprises a device operative to detect spectral changes through an inertial prediction.

9. The system of claim 1 where the weighting logic is further operative to derive a value from each of the weighted one or more of the tracked characteristics of the estimated noise in the received signal, that when compared to a predetermined threshold indicates a presence of speech.

10. The system of claim 1 where the weighting logic is applied to each of one or more of the tracked characteristics of the estimated noise in the received signal at each of the more than one frequency resolution, and the weighting logic is further operative to derive the value from the tracked characteristics of the estimated noise in the received signal at each of the more than one frequency resolution that when compared to the predetermined threshold indicates the presence of speech.

11. The system of claim 1 where the weighting logic comprises an A-weighting logic and a smoothing element operative to temporally smooth a noise-as-an-estimate-of-the-signal and to derive an indicator signal indicating the presence of speech.

12. The system of claim 1 further comprising a vehicle coupled to the spectrum monitor.

13. The system of claim 1 further comprising a voice activated system coupled to the spectrum monitor.

14. An enhancement system operative to estimate noise from a received signal comprising:

a spectrum monitor operative to divide a portion of a received signal into wide bands and narrow bands;

a global adaptation logic operative to derive a noise adaptation factor of the received signal;

a first and a second logic configured with inverse square functions operative to modify a plurality of noise adaptation rates based on a variance;

a third logic operative to modify the plurality of noise adaptation rates based on temporal characteristics;

a peer pressure logic operative to modify the plurality of noise adaptation rates and narrow band noise estimates based on trend characteristics and the modified noise adaptation rates of nearby wide bands and/or narrow bands; and

a temporal inertia logic operative to modify the plurality of noise adaptation rates and narrow band noise estimates based on predicted adaptation trends.

15. The system of claim 14 where the first logic comprises noise-as-an-estimate-of-the-signal logic.

16. The system of claim 14 where the second logic comprises temporal variability logic.

17. The system of claim 14 where the third logic comprises time-in-transient logic.

18. The system of claim 14 where the temporal characteristics comprise an amount of time a wide band signal estimate has been above a wide band noise estimate by a predetermined level.

19. The system of claim 14 where the peer pressure logic comprises weighting logic.

20. An enhancement system operative to estimate noise from a received signal comprising:

a spectrum monitor operative to divide a portion of a received signal into wide bands and narrow bands;

a normalizing logic operative to convert an estimate of the received signal into a near normal distribution;

a global adaptation logic operative to derive a noise adaptation factor of the received signal; and

means to modify wide band noise adaptation rates and narrow band noise estimates based on inverse square functions and temporal characteristics.

22. The enhancement system of claim 20 where a variance corresponds to the inverse square functions.

21. An enhancement method operative to estimate noise from a received signal comprising:

dividing a portion of a received signal into wide bands and narrow bands;

normalizing an estimate of the received signal into a near normal distribution;

deriving a noise adaptation factor of the received signal, where the noise adaptation factor is based on an inverse square function;

modifying a plurality of noise adaptation rates based on variances;

modifying the plurality of noise adaptation rates based on temporal characteristics; and

modifying the plurality of noise adaptation rates and narrow band noise estimates based on trend characteristics and the modified noise adaptation rates.