Voice-activity detection using energy ratios and periodicity

• US 20020165711A1
• Filed: 03/21/2001
• Published: 11/07/2002
• Est. Priority Date: 03/21/2001
• Status: Active Grant

• Current Assignee: Avaya Incorporated
• Original Assignee: Avaya Incorporated
• Inventors: Boland, Simon Daniel
• Granted Patent: US 7,171,357 B2
• Time in Patent Office: Days
• US Class Current: 704/231
• CPC Class Codes: G10L 2025/783 based on threshold decision
• 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

Abstract

A voice activity detector (100) filters (204) out noise energy and then computes a high-frequency (2400 Hz to 4000 Hz) versus low-frequency (100 Hz to 2400 Hz) signal energy ratio (224), total voiceband (100 Hz to 4000 Hz) signal energy (214), and signal periodicity (208) on successive frames of signal samples. Signal periodicity is determined by estimating the pitch period (206) of the signal, determining a gain value of the signal over the pitch period as a function of the estimated pitch period, and estimating a periodicity of the signal over the pitch period as a function of the estimated pitch period and the gain value. Voice is detected (230-232) in a segment if either (a) the difference between the average high-frequency versus low-frequency signal energy ratio and the present segment'"'"'s high-frequency versus low-frequency energy ratio either exceeds (310) a high threshold value or is exceeded (312) by a low threshold value, or (b) the average periodicity of the signal is lower (306) than a low threshold value, or (c) the difference between the average total signal energy and the present segment'"'"'s total energy exceeds (304) a threshold value and the average periodicity of the signal is lower (304) than a high threshold value, or (d) the average total signal energy exceeds (412) a minimum average total signal energy by a threshold value and voice has been detected (410) in the preceding segment.

Claims

1. A method of voice activity detection comprising:

determining a difference between (a) an average ratio of energy above a first threshold frequency in a signal comprising multiple frequencies and energy below the first threshold frequency in the signal and (b) a present ratio of energy above the first threshold frequency in the signal and energy below the first threshold frequency in the signal; and

in response to the difference either being exceeded by a first threshold value or exceeding a second threshold value greater than the first threshold value, indicating that the signal includes a voice signal.

2. The method of claim 1 wherein:

the first threshold frequency is about 2400 Hz.

3. The method of claim 1 further comprising:

prior to the determining, removing noise energy from the signal.

4. The method of claim 3 wherein:

removing comprises

filtering out from the signal frequencies below a second threshold frequency lower than the first threshold frequency.

5. The method of claim 4 wherein:

the second threshold frequency is about 100 Hz.

6. The method of claim 1 further comprising:

repeating the steps for successive segments of the signal.

7. The method of claim 1 further comprising:

determining an average periodicity of the signal; and

in response to the average periodicity of the signal being lower than a third threshold value, indicating that the signal includes a voice signal.

8. The method of claim 7 wherein:

determining an average periodicity comprises

estimating a pitch period of the signal;

determining a gain value of the signal over the pitch period as a function of the estimated pitch period;

determining a periodicity of the signal over the pitch period as a function of the estimated pitch period and the gain value; and

averaging the determined periodicity with previously-determined at least one said determined periodicity.

9. The method of claim 7 further comprising:

repeating the steps for successive segments of the signal.

10. The method of claim 7 further comprising:

determining a difference between average total energy in the signal and present total energy in the signal; and

in response to the difference between the average total energy and the present total energy being lower than a fourth threshold value and the average periodicity of the signal being lower than a fifth threshold value, indicating that the signal includes a voice signal.

11. The method of claim 10 further comprising:

prior to determining the difference between the average total energy and the present total energy, removing noise energy from the signal.

12. The method of claim 1 wherein:

determining a difference between the average total energy and the present total energy comprises

determining a difference between average total energy in a voiceband of the signal and present total energy in the voiceband.

13. The method of claim 12 wherein:

the voiceband extends from about 100 Hz to about 4000 Hz.

14. The method of claim 10 further comprising:

repeating the steps for successive segments of the signal.

15. The method of claim 14 further comprising:

in response to not indicating for a present segment of the signal that the signal includes a voice signal, and indicating for a segment of the signal preceding the present segment that the signal includes a voice signal, determining if the average total energy of the signal exceeds a minimum average total energy of the signal by a sixth threshold value; and

in response to the average total energy exceeding the minimum average total energy by the sixth threshold value, indicating that the signal includes a voice signal.

16. An apparatus that performs the method of any one of the claims 1-15.

17. A computer-readable medium containing executable instructions which, when executed in a computer, cause the computer to perform the method of any one of the claims 1-15.

19. The apparatus of claim 18 further comprising:

means for determining an average periodicity of the signal; and

means cooperative with the means for determining an average periodicity and responsive to the average periodicity being lower than a third threshold value, for indicating that the signal includes a voice signal.

20. The apparatus of claim 19 further comprising:

means for determining a difference between average total energy in the signal and present total energy in the signal; and

means cooperative with the means for determining a difference between the average total energy and the present total energy and the means for determining an average periodicity and responsive to the difference between the average total energy and the present total energy being lower than a fourth threshold value and the average periodicity of the signal being lower than the fifth threshold value, for indicating that the signal includes a voice signal.

21. The apparatus of claim 20 for detecting voice activity in successive segments of the signal, further comprising:

means responsive to a lack of indication for a present segment of the signal that the signal includes a voice signal and to an indication for a segment of the signal preceding the present segment that the signal includes a voice signal, for determining if the average total energy of the signal exceeds a minimum average total energy of the signal by a sixth threshold value; and

means cooperative with the means for determining of the average total energy exceeds the minimum average total energy and responsive to the average total energy exceeding the minimum average total energy by the sixth threshold value, for indicating that the signal includes a voice signal.

18. An apparatus for detecting voice activity comprising:

means for determining an average ratio of energy above a first threshold frequency in a signal comprising multiple frequencies and energy below the first threshold frequency in the signal;

means for determining a present ratio of energy above the first threshold frequency in the signal and energy below the first threshold frequency in the signal;

means for determining a difference between the average ratio and the present ratio; and

means cooperative with the means for determining a difference and responsive to the difference either being exceeded by a first threshold value or exceeding a second threshold value greater than the first threshold value, for indicating that the signal includes a voice signal.