Yule walker based low-complexity voice activity detector in noise suppression systems

• US 20080040109A1
• Filed: 08/03/2007
• Published: 02/14/2008
• Est. Priority Date: 08/10/2006
• Status: Active Grant

• Current Assignee: STMicroelectronics Asia Pacific Pte Limited (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Asia Pacific Pte Limited (STMicroelectronics NV)
• Inventors: Muralidhar, Karthik, Krishna, Anoop
• Granted Patent: US 8,775,168 B2
• Time in Patent Office: Days
• US Class Current: 704/233
• CPC Class Codes: G10L 25/87 Detection of discrete points within a voice signal

Abstract

A Yule-Walker based, low-complexity voice activity detector (VAD) is disclosed. An input signal is typically noisy speech (i.e., corrupted with, for example, babble noise). In one embodiment, a first initialization stage of the VAD computes an occurrence of a silent period within the input signal and the AR parameters. The VAD could accordingly compute a tentative adaptive threshold and output hypothesis H₁ (which means speech is present) during this stage. During the second initialization stage, the VAD generally builds a database of associated values and computes the adaptive threshold accordingly. The second initialization stage could also output tentative VAD decisions based on the tentative threshold computed in the first initialization stage. Finally, the VAD periodically retrains or updates AR parameters, threshold values and/or the database and outputs VAD decisions accordingly.

Claims

1. A method of detecting voice activity from an input signal having a silent period and a speech period, the method comprising:

determining an occurrence of an initial silent period;

computing an autoregressive (AR) parameter from the initial silent period;

storing information associated with the silent and speech periods in a database;

computing a threshold from the database; and

outputting a decision value based on at least one of;

the AR parameter, the threshold and the database.

2. The method of claim 1, wherein computing the AR parameter further comprises using a Yule-Walker relationship.

3. The method of claim 1 wherein computing the threshold further comprises computing an adaptive threshold using at least one of:

the AR parameters and the database.

4. The method of claim 3 further comprising:

periodically updating at least one of;

the AR parameter, the adaptive threshold value and the database.

5. The method of claim 3 further comprising:

periodically updating the adaptive threshold value at least once between one of two silent periods separated by a speech period and two speech periods separated by a silent period.

6. The method of claim 3, wherein the step of outputting further comprises outputting the decision value based on the adaptive threshold.

7. The method of claim 1 wherein the decision value is based on all of:

the AR parameter, the threshold and the database.

8. The method of claim 1 further comprising:

computing a tentative adaptive threshold from the initial silent period.

9. The method of claim 1 further comprising:

periodically updating the AR parameter when a second silent period has a duration greater than or equal to 30 blocks.

10. The method of claim 1, wherein the database comprises a logarithm of a smoothed local maxima of a test statistic of the input signal computed on a block by block basis.

11. A voice activity detector (VAD), comprising:

an input to receive a signal having a silent period and a speech period;

a first circuit configured to

determine an occurrence of an initial silent period,

compute an autoregressive (AR) parameter from an initial silent period, and

compute a threshold;

a memory to store a database of information associated with the silent and speech periods; and

a second circuit configured to output a decision value based on the threshold calculated in the first circuit.

12. The VAD of claim 11, wherein the first circuit is configured to compute the AR parameter using a Yule-Walker relationship.

13. The VAD of claim 11, wherein the second circuit is configured to compute an adaptive threshold using at least one of:

the AR parameters and the database.

14. The VAD of claim 13, further comprising a third circuit configured to output a decision value based on at least one of:

the AR parameter, the threshold and the database.

15. The VAD of claim 13, wherein the second circuit builds the database based on a test statistic of the input signal.

16. The VAD of claim 13, wherein the test statistic is computed using a Yule-Walker relationship.

17. The VAD of claim 13 further comprising a third circuit configured to periodically update the adaptive threshold value at least once between one of two silent periods separated by a speech period and two speech periods separated by a silent period.

18. The VAD of claim 11, wherein the first circuit is configured to compute a tentative adaptive threshold from the silent period.

19. The VAD of claim 11 further comprising a third circuit configured to periodically update the AR parameter when a second silent period has a duration greater than or equal to 30 blocks.

21. The method of claim 19 further comprising:

periodically updating at least one of;

the AR parameter, the adaptive threshold value and the database.

20. A method of using a voice activity detector (VAD), the method comprising:

receiving an input signal having a silent period and a speech period;

computing an autoregressive (AR) parameter from an initial silent period using a Yule-Walker relationship;

storing information associated with the silent period and the speech period in a database;

computing an adaptive threshold using at least one of;

the AR parameters and the database; and

outputting a decision value based on at least one of;

the AR parameter, the adaptive threshold and the database.