Detection of end of utterance in speech recognition system

• US 20050256711A1
• Filed: 05/12/2004
• Published: 11/17/2005
• Est. Priority Date: 05/12/2004
• Status: Active Grant

• Current Assignee: Conversant Wireless Licensing S.à.r.l. (f/k/a Core Wireless Licensing S.a.r.l.) (MOSAID Technologies Inc. (f/k/a Conversant Intellectual Property Management))
• Original Assignee: 2011 Intellectual Property Asset Trust (Nokia Corporation)
• Inventors: Lahti, Tommi
• Granted Patent: US 9,117,460 B2
• Time in Patent Office: Days
• US Class Current: 704/253
• CPC Class Codes: G10L 25/87 Detection of discrete points within a voice signal

Abstract

The present invention relates to speech recognition systems, especially to arranging detection of end-of utterance in such systems. A speech recognizer of the system is configured to determine whether recognition result determined from received speech data is stabilized. The speech recognizer is configured to process values of best state scores and best token scores associated with frames of received speech data for end of utterance detection purposes. Further, the speech recognizer is configured to determine whether end of utterance is detected or not, based on the processing, if the recognition result is stabilized.

Claims

1. A speech recognition system comprising a speech recognizer with end of utterance detection, wherein the speech recognizer is configured to determine whether recognition result determined from received speech data is stabilized,

the speech recognizer is configured to process values of best state scores and best token scores associated with frames of received speech data for end of utterance detection purposes, and

the speech recognizer is configured to determine whether end of utterance is detected or not, based on the processing, if the recognition result is stabilized.

2. A speech recognition system according to claim 1, wherein the speech recognizer is configured to calculate the best state score sum by summing the best state score values of a pre-determined number of frames,

in response to the recognition result being stabilized, the speech recognizer is configured to compare the best state score sum to a predetermined threshold sum value, and

the speech recognizer is configured to determine detection of end of utterance if the best state score sum does not exceed the threshold sum value.

3. A speech recognition system according to claim 2, wherein the speech recognizer is configured to normalize the best score sum by the number of detected silence models, and

the speech recognizer is configured to compare the normalized best state score sum to the pre-determined threshold sum value.

4. A speech recognition system according to claim 2, wherein the speech recognizer is further configured to compare the number of best state score sums exceeding the threshold sum value to a predetermined minimum number value defining the required minimum number of best state score sums exceeding the threshold sum value, and

the speech recognizer is configured to determine detection of end of utterance if the number of best state score sums exceeding the threshold sum value is the same or larger than the predetermined minimum number value.

5. A speech recognition system according to claim 1, wherein the speech recognizer is configured to wait a pre-determined time period before determining detection of end of utterance.

6. A speech recognition system according to claim 1, wherein the speech recognizer is configured to determine best token score values repetitively,

the speech recognizer is configured to calculate the slope of the best token score values based on at least two best token score values,

the speech recognizer is configured to compare the slope to a pre-determined threshold slope value, and

the speech recognizer is configured to determine detection of end of utterance if the slope does not exceed the threshold slope value.

7. A speech recognition system according to claim 6, wherein the slope is calculated for each frame.

8. A speech recognition system according to claim 6, wherein the speech recognizer is further configured to compare the number of slopes exceeding the threshold slope value to a predetermined minimum number of slopes exceeding the threshold slope value, and

the speech recognizer is configured to determine detection of end of utterance if the number of best state score sums exceeding the threshold slope value is the same or larger than the predetermined minimum number.

9. A speech recognition system according to claim 6, wherein the speech recognizer is configured to begin slope calculations only after a pre-determined number of frames has been received.

10. A speech recognition system according to claim 1, wherein the speech recognizer is configured to determine best token score of at least one inter-word token and best token score of an exit token, and

the speech recognizer is configured to determine detection of end of utterance only if the best token score value of the exit token is higher than the best token score of the inter-word token.

11. A speech recognition system according to claim 1, wherein the speech recognizer is configured to determine detection of end of utterance only if the recognition result is not rejected.

12. A speech recognition system according to claim 1, wherein the speech recognizer is configured to determine detection of end of utterance after a maximum number of frames producing substantially the same recognition result has been received.

13. A method for arranging detection of end-of utterance in a speech recognition system, the method comprising:

processing values of best state scores and best token scores associated with frames of received speech data for end of utterance detection purposes,

determining whether recognition result determined from received speech data is stabilized, and

determining whether end of utterance is detected or not, based on the processing, if the recognition result is stabilized.

14. A method according to claim 13, wherein the best state score sum is calculated by summing the best state score values of a pre-determined number of frames,

in response to the recognition result being stabilized, the best state score sum is compared to a predetermined threshold sum value, and

the detection of end of utterance is determined if the best state score sum does not exceed the threshold sum value.

15. A method according to claim 13, wherein best token score values are determined repetitively,

the slope of the best token score values is calculated based on at least two best token score values,

the slope is compared to a pre-determined threshold slope value, and

the detection of end of utterance is determined if the slope does not exceed the threshold slope value.

16. A method according to claim 13, wherein best token score of at least one inter-word token and best token score of an exit token are determined, and

the detection of end of utterance is determined only if the best token score value of the exit token is higher than the best token score of the inter-word token.

17. A method according to claim 13, wherein the detection of end of utterance is determined only if the recognition result is not rejected.

18. An electronic device comprising a speech recognizer, wherein the speech recognizer is configured to determine whether recognition result determined from received speech data is stabilized,

the speech recognizer is configured to process values of best state scores and best token scores associated with frames of received speech data for end of utterance detection purposes, and

the speech recognizer is configured to determine whether end of utterance is detected or not, based on the processing, if the recognition result is stabilized.

19. An electronic device according to claim 18, wherein the speech recognizer is configured to calculate the best state score sum by summing the best state score values of a pre-determined number of frames,

in response to the recognition result being stabilized, the speech recognizer is configured to compare the best state score sum to a predetermined threshold sum value, and

the speech recognizer is configured to determine detection of end of utterance if the best state score sum does not exceed the threshold sum value.

20. An electronic device according to claim 19, wherein the speech recognizer is configured to normalize the best score sum by the number of detected silence models, and

the speech recognizer is configured to compare the normalized best state score sum to the pre-determined threshold sum value.

21. An electronic device according to claim 19, wherein the speech recognizer is further configured to compare the number of best state score sums exceeding the threshold sum value to a predetermined minimum number value defining the required minimum number of best state score sums exceeding the threshold sum value, and

the speech recognizer is configured to determine detection of end of utterance if the number of best state score sums exceeding the threshold sum value is the same or larger than the predetermined minimum number value.

22. An electronic device according to claim 18, wherein the speech recognizer is configured to wait a pre-determined time period before determining detection of end of utterance.

23. An electronic device according to claim 18, wherein the speech recognizer is configured to determine best token score values repetitively,

the speech recognizer is configured to calculate the slope of the best token score values based on at least two best token score values,

the speech recognizer is configured to compare the slope to a pre-determined threshold slope value, and

the speech recognizer is configured to determine detection of end of utterance if the slope does not exceed the threshold slope value.

24. An electronic device according to claim 23, wherein the slope is calculated for each frame.

25. An electronic device according to claim 23, wherein the speech recognizer is further configured to compare the number of slopes exceeding the threshold slope value to a predetermined minimum number of slopes exceeding the threshold slope value, and

the speech recognizer is configured to determine detection of end of utterance if the number of best state score sums exceeding the threshold slope value is the same or larger than the predetermined minimum number.

26. An electronic device according to claim 23, wherein the speech recognizer is configured to begin slope calculations only after a pre-determined number of frames has been received.

27. An electronic device according to claim 18, wherein the speech recognizer is configured to determine best token score of at least one inter-word token and best token score of an exit token, and

the speech recognizer is configured to determine detection of end of utterance only if the best token score value of the exit token is higher than the best token score of the inter-word token.

28. An electronic device according to claim 18, wherein the speech recognizer is configured to determine detection of end of utterance only if the recognition result is not rejected.

29. An electronic device according to claim 18, wherein the speech recognizer is configured to determine detection of end of utterance after a maximum number of frames producing substantially the same recognition result has been received.

30. An electronic device according to claim 18, wherein the electronic device is a mobile phone or a PDA device.

31. A computer program product, loadable into the memory of a data processing device, for arranging detection of end-of utterance in an electronic device comprising a speech recognizer, the computer program product comprising:

program code for processing values of best state scores and best token scores associated with frames of received speech data for end of utterance detection purposes,

program code for determining whether recognition result determined from received speech data is stabilized, and

program code for determining whether end of utterance is detected or not, based on the processing, if the recognition result is stabilized.