Method of measuring degree of enhancement to voice signal

• US 7,818,168 B1
• Filed: 12/01/2006
• Issued: 10/19/2010
• Est. Priority Date: 12/01/2006
• Status: Active Grant

• Current Assignee: National Security Agency
• Original Assignee: The United States of America As Represented By The Director National Security Agency
• Inventors: Cusmariu, Adolf
• Primary Examiner(s): Smits; Talivaldis Ivars
• Assistant Examiner(s): BORSETTI, GREG
• Application Number:
  US11/645,264
• Time in Patent Office: 1,418 Days
• Field of Search: 704/208, 704/209, 704/E21.002, 704/220, 704/225, 381/71.14
• US Class Current: 704/209
• CPC Class Codes: G10L 21/0364 for improving intelligibility

Abstract

A method of measuring the degree of enhancement made to a voice signal by receiving the voice signal, identifying formant regions in the voice signal, computing stationarity for each identified formant region, enhancing the voice signal, identifying formant regions in the enhanced voice signal that correspond to those identified in the received voice signal, computing stationarity for each formant region identified in the enhanced voice signal, comparing corresponding stationarity results for the received and enhanced voice signals, and calculating at least one user-definable statistic of the comparison results as the degree of enhancement made to the received voice signal.

Claims

1. A method of measuring the degree of enhancement made to a voice signal, comprising the steps of:

a) receiving, on a digital signal processor, the voice signal;

b) identifying, on the digital signal processor, a user-definable number of formant regions in the voice signal;

c) computing, on the digital signal processor, stationarity for each formant region identified in the voice signal;

d) enhancing, on the digital signal processor, the voice signal;

e) identifying, on the digital signal processor, formant regions in the enhanced voice signal that correspond to those identified in step (b);

f) computing, on the digital signal processor, stationarity for each formant region identified in the enhanced voice signal;

g) comparing, on the digital signal processor, corresponding results of step (c) and step

(f); and

h) calculating, on the digital signal processor, at least one user-definable statistic of the results of step (g) as the degree of enhancement made to the voice signal.

2. The method of claim 1, further including the step of digitizing the received voice signal if the signal is received in analog format.

3. The method of claim 1, further including the step of segmenting the received voice signal into a user-definable number of segments.

4. The method of claim 1, wherein each step of identifying formant regions is comprised of the step of identifying formant regions using an estimate of a Cepstrum.

5. The method of claim 4, wherein the step of estimating a Cepstrum is comprised of selecting from the group of Cepstrum estimations consisting of a real Cepstrum and an absolute value of a complex Cepstrum.

6. The method of claim 1, wherein each step of computing stationarity for each formant region is comprised of the steps of:

i) calculating an arithmetic average of the formant region;

ii) calculating a geometric average of the formant region;

iii) calculating a harmonic average of the formant region; and

iv) comparing any user-definable combination of two results of step (i), step (ii), and step (iii).

7. The method of claim 6, wherein the step of comparing any user-definable combination of two results of step (i), step (ii), and step (iii) is comprised of the step of comparing any user-definable combination of two results of step (i), step (ii), and step (iii) using a comparison method selected from the group of comparison methods consisting of difference, difference divided by sum, and difference divided by one plus the difference.

8. The method of claim 1, wherein each step of enhancing the voice signal is comprised of enhancing the voice signal using a voice enhancement method selected from the group of voice enhancement methods consisting of, echo cancellation, delay-time minimization, and volume control.

9. The method of claim 1, wherein the step of comparing corresponding results of step (c) and step (f) is comprised of comparing corresponding results of step (c) and step (f) using a comparison method selected from the group of comparison methods consisting of a ratio of corresponding results of step (c) and step (f) minus one and a difference of corresponding results of step (c) and step (f) divided by a sum of corresponding results of step (c) and step (f).

10. The method of claim 1, wherein the step of calculating at least one user-definable statistic of the results of step (g) is comprised of calculating at least one user-definable statistic of the results of step (g) using a statistical method selected from the group of statistical methods consisting of arithmetic average, median, and maximum value.

11. The method of claim 2, further including the step of segmenting the received voice signal into a user-definable number of segments.

12. The method of claim 11, wherein each step of identifying formant regions is comprised of the step of identifying formant regions using an estimate of a Cepstrum.

13. The method of claim 12, wherein the step of estimating a Cepstrum is comprised of selecting from the group of Cepstrum estimations consisting of a real Cepstrum and an absolute value of a complex Cepstrum.

14. The method of claim 13, wherein each step of computing stationarity for each formant region is comprised of the steps of:

i) calculating an arithmetic average of the formant region;

ii) calculating a geometric average of the formant region;

iii) calculating a harmonic average of the formant region; and

iv) comparing any user-definable combination of two results of step (i), step (ii), and step (iii).

15. The method of claim 14, wherein the step of comparing any user-definable combination of two results of step (i), step (ii), and step (iii) is comprised of the step of comparing any user-definable combination of two results of step (i), step (ii), and step (iii) using a comparison method selected from the group of comparison methods consisting of difference, ratio, difference divided by stun, and difference divided by one plus the difference.

16. The method of claim 15, wherein each step of enhancing the voice signal is comprised of enhancing the voice signal using a voice enhancement method selected from the group of voice enhancement methods consisting of echo cancellation, delay-time minimization, and volume control.

17. The method of claim 16, wherein the step of comparing corresponding results of step (c) and step (f) is comprised of comparing corresponding results of step (c) and step (f) using a comparison method selected from the group of comparison methods consisting of a ratio of corresponding results of step (c) and step (f) minus one and a difference of corresponding results of step (c) and step (f) divided by a sum of corresponding results of step (c) and step (f).

18. The method of claim 17, wherein the step of calculating at least one user-definable statistic of the results of step (g) is comprised of calculating at least one user-definable statistic of the results of step (g) using a statistical method selected from the group of statistical methods consisting of arithmetic average, median, and maximum value.