Method and apparatus for detecting voice activity in a speech signal

• US 6,188,981 B1
• Filed: 09/18/1998
• Issued: 02/13/2001
• Est. Priority Date: 09/18/1998
• Status: Expired due to Term

• Current Assignee: HTC Corporation
• Original Assignee: Conexant Systems Incorporated (Synaptics Incorporated)
• Inventors: Benyassine, Adil, Shlomot, Eyal
• Primary Examiner(s): Smits, Talivaldis I.
• Assistant Examiner(s): Nolan, Daniel A.
• Application Number:
  US09/156,416
• Time in Patent Office: 879 Days
• Field of Search: 704/233, 704/219, 704/246, 704/214, 704/240, 704/243, 704/231, 704/207, 709/247
• US Class Current: 704/233
• 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 method and apparatus for generating frame voicing decisions for an incoming speech signal having periods of active voice and non-active voice for a speech encoder in a speech communications system. A predetermined set of parameters is extracted from the incoming speech signal, including a pitch gain and a pitch lag. A frame voicing decision is made for each frame of the incoming speech signal according to values calculated from the extracted parameters. The predetermined set of parameters further includes a frame full band energy, and a set of spectral parameters called Line Spectral Frequencies (LSF).

Claims

1. In a speech communication system, a method for generating a frame voicing decision, the steps of the method comprising:

extracting a set of parameters, including pitch gain and pitch lag, from an incoming speech signal, for each frame;

calculating a standard deviation of the pitch lag from the extracted parameters over a consecutive number of subframes;

calculating a long term average of the pitch gain from the extracted parameters; and

making a frame voicing decision according to the results of said calculation step.

2. The method according to claim 1, wherein the extracted set of parameters further comprises a full band energy and line spectral frequencies (LSF).

3. The method according to claim 2, further comprising the steps of:

calculating a short-term average of energy E, {overscore (E)}s;

calculating a short-term average of {overscore (LSF)}s;

calculating an average energy {overscore (E)}; and

calculating an average LSF value, {overscore (LSF)}n.

4. The method according to claim 3, further comprising the steps of:

calculating a spectral difference SD₁ using a normalized Itakura-Saito measure;

calculating a spectral difference SD₂ using a mean square error method;

calculating a spectral difference SD₃ using a mean square error method; and

calculating a long-term mean of SD₂.

5. The method according to claim 4, wherein the frame voicing decision is made based on the calculated values.

6. The method according to claim 5, further comprising the step of smoothing the frame voicing decision.

7. The method according to claim 6, further comprising the step of performing an initialization for a predetermined number of initial frames, such that the voicing decision is set to active voice or non-active voice.

8. A Voice Activity Detector (VAD) for making a voicing decision on an incoming speech signal frame, the VAD comprising:

an extractor for extracting a set of parameters, including pitch gain and pitch lag, from the incoming speech signal for each frame;

a calculator unit for calculating a standard deviation of the pitch lag from the extracted parameters over a consecutive number of subframes and a long term mean pitch gain from the extracted parameters; and

a decision unit for making a frame voicing decision according to the results from the calculator unit.

9. The VAD according to claim 8, wherein the extractor also extracts the parameters full band energy and line spectral frequencies (LSF).

10. The VAD according to claim 9, wherein the calculator unit further calculates:

a short-term average of energy E, {overscore (E)}s;

a short-term average of LSF, {overscore (LSF)}s;

an average energy {overscore (E)}; and

an average LSF value, {overscore (LSFN+L )}.

11. The VAD according to claim 10, wherein the calculator unit further calculates:

a spectral difference SD₁ using a normalized Itakura-Saito measure;

a spectral difference SD₂ using a mean square error method;

a spectral difference SD₃ using a mean square error method; and

a long-term mean of SD₂.

12. The VAD according to claim 11, wherein the decision unit makes a frame voicing decision according to the values calculated by the calculator unit.

13. The VAD according to claim 12, wherein the voicing decision is smoothed.