Formants extracting method

• US 20050075864A1
• Filed: 10/06/2004
• Published: 04/07/2005
• Est. Priority Date: 10/06/2003
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Kim, Chan-Woo
• Granted Patent: US 8,000,959 B2
• Time in Patent Office: Days
• US Class Current: 704/206
• CPC Class Codes: G10L 25/15 the extracted parameters being formant information
• CPC Class Codes: G10L 25/48 specially adapted for particular use

Abstract

In a formants extracting method capable of precisely obtaining formants as resonance frequencies of voice with less computational complexity, the method includes searching a maximum value by a spectral peak-picking method, judging whether the number of formants corresponding to a zero at the obtained maximum point are two, and analyzing a pertinent root by roots polishing when the number of the formants are judged as two. The number of the formants are judged by applying Cauchy'"'"'s integral formula, wherein Cauchy'"'"'s integral formula is not applied repeatedly but only once at a surrounding portion of the maximum value in a z-domain.

Claims

1. A formants extracting method, comprising:

obtaining a maximum value in a spectrum;

judging whether the number of formants corresponding to a zero at a maximum point are two; and

analyzing a root by roots polishing when the number of formants are judged as two.

2. The method of claim 1, wherein the maximum value is obtained by a spectral peak-picking method.

3. The method of claim 1, wherein the number of formants are obtained by applying Cauchy'"'"'s integral formula.

4. The method of claim 3, wherein Cauchy'"'"'s integral formula is applied to a surrounding area of a point having a maximum value in a specific region.

5. The method of claim 4, wherein the specific region is a z-domain.

6. The method of claim 1, wherein the root is a zero corresponding to the number of formants judged as two.

7. The method of claim 1, wherein Bairstow'"'"'s algorithm is used in the roots polishing.

8. The method of claim 1, wherein an approximation method is used in the roots polishing.

9. The method of claim 1, wherein the extracted formants are used as a feature vector of voice recognition.

10. The method of claim 1, wherein the extracted formants are used for a formants vocoder.

11. In receiving a voice signal and analyzing it, a formants extracting method, comprising:

receiving a frame of a new voice signal;

pre-processing the received voice signal;

multiplying a window function by an appropriate range of the pre-processed voice signal to extract a short-time signal;

obtaining a linear prediction coefficient from the extracted short-time signal and obtaining a specific spectrum therefrom;

searching maximum points in the specific spectrum and judging whether the maximum points are possibly related to at least two formants;

discriminating that the maximum points are actually related to the at least two formants; and

analyzing a pertinent root by roots polishing when the maximum points are actually related to the at least two formants.

12. The method of claim 11, wherein pre-processing the received voice signal comprises filtering the received voice signal.

13. The method of claim 11, wherein pre-processing the received voice signal comprises enhancing the received voice signal.

14. The method of claim 11, wherein pre-processing the received voice signal comprises passing the received voice signal through a pre-emphasis filter.

15. The method of claim 11, wherein the appropriate range of the voice signal is approximately 20 ms˜

40 ms.

16. The method of claim 11, wherein the window function is a Hamming window function.

17. The method of claim 11, wherein the window function is a Kaiser window function.

18. The method of claim 11, wherein the window function is a Blackmann function.

19. The method of claim 11, wherein the specific spectrum is a linear prediction spectrum.

20. The method of claim 11, wherein the specific spectrum is a spectrum equalized by a cepstrum.

21. The method of claim 11, wherein Cauchy'"'"'s integral formula is used to judge whether the maximum points are actually related to the at least two formants.

22. The method of claim 21, wherein Cauchy'"'"'s integral formula is applied to a surrounding portion of a maximum value in a specific region.

23. The method of claim 22, wherein the specific region is a z-domain.

24. The method of claim 11, wherein Bairstow'"'"'s algorithm is used in the roots polishing.

25. The method of claim 11, wherein a root approximation method is used in the roots polishing.

26. The method of claim 11, wherein the root is a zero corresponding to the number of formants judged as two.

27. The method of claim 11, wherein the extracted formants are used as a feature vector of voice recognition.

28. The method of claim 11, wherein the extracted formants are used for a formants vocoder.