MULTIPLE MICROPHONE BASED LOW COMPLEXITY PITCH DETECTOR

• US 20130117014A1
• Filed: 11/07/2011
• Published: 05/09/2013
• Est. Priority Date: 11/07/2011
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Zhang, Xianxian, Lunardhi, Alfonsus
• Granted Patent: US 8,751,220 B2
• Time in Patent Office: Days
• US Class Current: 704/207
• CPC Class Codes: G10L 2021/02165 Two microphones, one receiving mainly the noise signal and the other one mainly the speech signal
• CPC Class Codes: G10L 21/00 Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility G10L19/00 takes precedence
• CPC Class Codes: G10L 25/90 Pitch determination of speech signals

Abstract

Disclosed are various embodiments of multiple microphone based pitch detection. In one embodiment, a method includes obtaining a primary signal and a secondary signal associated with multiple microphones. A pitch value is determined based at least in part upon a level difference between the primary and secondary signals. In another embodiment, a system includes a plurality of microphones configured to provide a primary signal and a secondary signal. A level difference detector is configured to determine a level difference between the primary and secondary signals and a pitch identifier is configured to clip the primary and secondary signals based at least in part upon the level difference. In another embodiment, a method determines the presence of voice activity based upon a pitch prediction gain variation that is determined based at least in part upon a pitch lag.

Claims

1. A method, comprising:

obtaining a primary signal corresponding to a primary microphone and a secondary signal corresponding to a secondary microphone;

determining a level difference between the primary and secondary signals; and

determining a pitch value based at least in part upon the determined level difference of the primary and secondary signals.

2. The method of claim 1, wherein determining the pitch value includes determining a clipping level based upon the level difference.

3. The method of claim 2, wherein determining the pitch value further includes:

clipping a portion of the primary signal using the determined clipping level; and

determining a pitch value associated with the portion of the primary signal based upon autocorrelation of the clipped portion of the primary signal.

4. The method of claim 3, wherein determining the pitch value further includes determining a clipping level for the secondary signal based upon the level difference.

5. The method of claim 4, wherein determining the pitch value further includes:

clipping a portion of the secondary signal using the determined clipping level for the secondary signal; and

determining a pitch value associated with the portion of the secondary signal based upon autocorrelation of the clipped portion of the secondary signal.

6. The method of claim 5, wherein determining the pitch value further includes determining a final pitch value based upon the pitch value associated with the primary signal and the pitch value associated with the secondary signal.

7. The method of claim 3, wherein the primary and secondary signals are sectioned to provide the portion of the primary signal and a corresponding portion of the secondary signal.

8. The method of claim 2, wherein a ratio of the averaged Teager Energy Operator (TEO) energy (R_TEO) of the primary and secondary signals represents the level difference between the primary and secondary signals.

9. The method of claim 8, wherein the clipping level is based at least in part upon an adaptive factor that varies between a minimum value and a maximum value based upon the R_TEO.

10. The method of claim 8, wherein the adaptive factor varies exponentially within a defined range of the R_TEO.

11. A system, comprising:

a plurality of microphones configured to provide a primary signal and a secondary signal;

a level difference detector configured to determine a level difference between the primary and secondary signals; and

a pitch identifier configured to clip the primary and secondary signals based at least in part upon the level difference.

12. The system of claim 11, wherein the pitch identifier is further configured to determine a pitch value based at least in part upon autocorrelation of the clipped primary signal and autocorrelation of the clipped secondary signal.

13. The system of claim 11, wherein the pitch identifier is further configured to determine a clipping level based at least in part upon the level difference.

14. The system of claim 13, wherein the level difference is a ratio of the averaged Teager Energy Operator (TEO) energy (R_TEO) of the primary and secondary signals.

15. The system of claim 13, wherein the primary and secondary signals are sectioned into a plurality of corresponding signal sections before clipping, each signal section including a pitch searching frame and a portion that overlaps with an adjacent signal section.

16. The system of claim 11, wherein a primary microphone provides the primary signal and a noise reference microphone provides the secondary signal.

17. The system of claim 11, wherein a speech output of a beamformer provides the primary signal based upon signals from the plurality of microphones and a noise output of a beamformer provides the secondary signal based upon the signals from the plurality of microphones.

18. A method, comprising:

obtaining a section of a primary signal and a corresponding section of a secondary signal, the primary and secondary signals associated with a plurality of microphones;

determining a pitch value based at least in part upon a level difference between the primary signal and secondary signal;

determining a pitch lag based upon the pitch value;

determining a pitch prediction gain variation for the primary signal section based at least in part upon the pitch lag; and

determine the presence of voice activity based upon the pitch prediction gain variation.

19. The method of claim 18, wherein the pitch prediction gain variation is determined with a pitch searching frame of the primary signal section.

20. The method of claim 18, wherein the pitch prediction gain variation is compared to a predefined threshold to determine the presence of voice activity.