APPARATUS AND METHOD FOR RECOGNIZING VOICE WITH REDUCED SENSITIVITY TO AMBIENT NOISE

• US 20010029449A1
• Filed: 07/21/1997
• Published: 10/11/2001
• Est. Priority Date: 02/09/1990
• Status: Active Grant

• Current Assignee: Masayuki Iida, Ryuji Suzuki, Shin-Ichi Tsurufuji
• Original Assignee: Masayuki Iida, Ryuji Suzuki, Shin-Ichi Tsurufuji
• Inventors: IIDA, MASAYUKI, SUZUKI, RYUJI, TSURUFUJI, SHIN-ICHI
• Granted Patent: US 6,411,928 B2
• Time in Patent Office: Days
• US Class Current: 704/226
• CPC Class Codes: G10L 15/10 using distance or distortion measures between unknown speech and reference templates
• CPC Class Codes: G10L 15/20 Speech recognition techniques specially adapted for robustness in adverse environments, e.g. in noise, of stress induced speech G10L21/02 takes precedence

Abstract

A voice recognizing apparatus includes a filter bank for deriving feature parameters of voice from a microphone and a filter bank for deriving feature parameters of noise represented by an electric signal which is directly inputted to a terminal. The voice parameters and the noise parameters are respectively stored in a voice parameter buffer and a noise parameter buffer. A threshold value for sampling the voice parameters is set to be changed in accordance with a noise level for each frame. From a series of the voice parameters exceeding the threshold value, a series of the noise parameters corresponding thereto are subtracted so that only a voice parameter pattern can be obtained. In a recognition mode, the voice pattern is compared with a reference pattern to recognize the voice from the microphone. In addition, in a registration mode, the voice pattern is registered as a reference pattern.

Claims

1. A voice recognizing apparatus, comprising:

a microphone for inputting voice;

sampling means for detecting a boundary of a voice signal from said microphone exceeding a threshold value; and

changing means for changing said threshold value in accordance with a level of ambient noise.

2. A voice recognizing apparatus in accordance with

claim 1

, further comprising invalidating means for invalidating said sampling means when a level of said ambient noise is large.

3. A voice recognizing apparatus in accordance with

claim 2

, wherein said sampling means samples said voice signal exceeding said threshold value through 2 stages.

4. A voice recognizing apparatus in accordance with

claim 1

, further comprising recognizing means for recognizing the voice signal sampled by said sampling means.

5. A voice recognizing apparatus in accordance with

claim 4

, wherein said recognizing means includes standard changing means for changing a determination standard of recognition in accordance with a level of said ambient noise.

6. A voice recognizing apparatus in accordance with

claim 1

, further comprising registering means for registering a reference pattern on the basis of the sound signal sampled by said sampling means.

7. A voice recognizing apparatus in accordance with

claim 6

, further comprising invalidating means for substantially invalidating said registering means when the level of said ambient noise is large.

8. A voice recognizing apparatus in accordance with

claim 1

, wherein said changing means includes means for setting said threshold value in accordance with a level of the voice signal from said microphone when a level of said ambient noise is below a predetermined value.

9. A voice recognizing apparatus, comprising:

a microphone for inputting voice; and

changing means for changing a threshold value for sampling a voice signal from said microphone in accordance with a level of ambient noise.

10. A voice recognizing apparatus in accordance with

claim 9

, further comprising mode setting means for setting a first mode wherein the voice signal from said microphone is to be processed or a second mode wherein the voice signal from said microphone is not to be processed;

and means for setting a threshold value which is utilized in said first mode on the basis of the voice signal from said microphone when said second mode is set.

11. A voice recognizing method comprising steps of:

(a) detecting a level of ambient noise;

(b) variably changing a threshold value in accordance with the level of the ambient noise as detected; and

(c) detecting a boundary of a voice signal inputted from a microphone in accordance with the threshold value;

12. A voice recognizing method in accordance with

claim 11

, further comprising a step of (d) recognizing a voice signal as sampled.

13. A voice recognizing method in accordance with

claim 11

, further comprising a step of (e) registering a reference pattern on the basis of the voice signal as sampled.

14. A voice recognizing method comprising of steps:

(a) detecting a level of ambient noise; and

(b) variably setting threshold value for sampling a voice signal from a microphone in accordance with the level of the ambient noise as detected.

15. A voice recognizing apparatus, comprising:

a microphone to which voice to be recognized is inputted;

first sampling means for sampling a feature parameter of a voice signal from said microphone for each frame with a predetermined time interval;

first converting means for converting said feature parameter sampled by said first sampling means into first feature parameter data;

first memory means for storing said first feature parameter data outputted from said first converting means for a plurality of frames;

first reading means for reading a series of said first feature parameter data exceeding a threshold value from said first memory means;

noise level detecting means for detecting a level of ambient noise; and

threshold value setting means for variably setting said threshold value in accordance with an amplitude of the level of said ambient noise.

16. A voice recognizing apparatus in accordance with

claim 15

, where said threshold value setting means includes means for setting said threshold value on the basis of power data of said voice signal inputted from said microphone when said level of said ambient noise is small.

17. A voice recognizing apparatus in accordance with

claim 15

, wherein said threshold value setting means includes weighted mean value calculation means for calculating a weighted mean value of said threshold value.

18. A voice recognizing apparatus in accordance with

claim 17

, further comprising second memory means for storing said threshold value set by said threshold value setting means for each frame;

wherein said weighted mean value calculation means calculate a weighted mean value one or more threshold values of one or more prior frames read from said second memory means and a threshold value of a current frame.

19. A voice recognizing apparatus in accordance with

claim 18

, further comprising detecting means for detecting whether or not said level of said ambient noise increases;

wherein said weighted mean value calculation means sets a weight of the threshold value of said current frame to be larger than a weight of the threshold values of said prior frames when said detecting means detects that said level of said ambient noise increase.

20. A voice recognizing apparatus in accordance with

claim 19

, wherein said weighted mean value calculation means sets a weight of the threshold value of said current frame to be smaller than a weight of the threshold values of said prior frames when said detecting means does not detect that said level of said ambient noise increases.

21. A voice recognizing apparatus in accordance with

claim 17

, further comprising detecting means for detecting whether or not a level of said ambient noise increases;

wherein weighted mean value calculation means sets a weight of the threshold value of said current frame to be smaller than a weight of the threshold values of said prior frames when said detecting means does not detect that said levels of said ambient noise increases.

22. A voice recognizing apparatus accordance with

claim 15

, further comprising invalidating means for invalidating said first reading means when the level of said ambient noise is more than a predetermined value.

23. A voice recognizing apparatus in accordance with

claim 15

, further comprising first and second address storing means for respectively storing a head frame and a tail frame of said first feature parameter data read from said first memory means by said first reading means.

24. A voice recognizing apparatus in accordance with

claim 23

, further comprising address determining means for determining a true head frame address and a true tail frame address on the basis of said head frame address and said tail frame address respectively stored in said first and second address storing means;

wherein said first reading means reads said first feature parameter data from said first memory means from said true head frame address to id true tail frame address.

25. A voice recognizing apparatus in accordance with

claim 24

, wherein said address determining means includes means for determining an address of said first memory means which is prior to said head frame address stored in said first address storing means and stores a minimum value as said true head frame address and an address of said first memory means which is after said head frame address stored in said first address storing means and stores a minimum value as said true tail frame address.

26. A voice recognizing apparatus in accordance with

claim 15

, further comprising:

second sampling means for sampling a feature parameter of a signal representative of said ambient noise for each frame with said predetermined time interval;

second converting means for converting said feature parameter sampled by said second sampling means into second feature parameter data;

second memory means for storing said second feature parameter data outputted from said second converting means for a plurality of frames;

second reading means for reading said second feature parameter data from an address of said second memory means corresponding to that of said first memory means which is read by said first reading means; and

subtracting means for subtracting said second feature parameter data from said first feature parameter data.

27. A voice recognizing apparatus in accordance with

claim 26

, wherein said second reading means reads said second feature parameter data from an address of said second memory means equal to a frame which is delayed from a frame corresponding to an address of said first memory means which is read by said first reading means.

28. A voice recognizing apparatus in accordance with

claim 26

, wherein said subtracting means subtracts said second feature parameter data read from said second memory means which is multiplied by a predetermined constant from said first feature parameter data.

29. A voice recognizing apparatus in accordance with

claim 26

, further comparing recognition means for recognizing the voice inputted from said microphone on the basis of a subtraction result by said subtracting means.

30. A voice recognizing apparatus in accordance with

claim 29

, further comprising first invalidating means for invalidating substantially said recognition means when said level of said ambient noise is large.

31. A voice recognizing apparatus in accordance with

claim 26

, further comprising registration means for registering a feature parameter pattern of the voice inputted from said microphone on the basis of a subtraction result of said subtracting means.

32. A voice recognizing apparatus in accordance with

claim 31

, further comprising second invalidating means for invalidating substantially said registration means when said level of said ambient noise is large.

33. A voice recognizing apparatus in accordance with

claim 15

or

26

, wherein said ambient noise is generated from a loudspeaker in response to an audio signal from an audio equipment, and said ambient noise level detecting means includes audio signal inputting means for directly inputting said audio signal from said audio equipment.

34. A voice recognizing apparatus in accordance with

claim 33

, further comprising recognition means for recognizing the voice inputted from said microphone through a comparison of said first feature parameter data read by said first reading means and a reference pattern.

35. A voice recognizing apparatus in accordance with

claim 34

, further comprising controlling means for controlling said audio equipment in response to a recognition result of said recognition means.

36. A voice recognizing apparatus in accordance with

claim 15

, wherein said threshold value setting means includes means for setting said threshold value in accordance with a level of a voice signal from said microphone when said level of said ambient noise is below a predetermined value.

37. A voice recognizing apparatus in accordance with

claim 15

, further comprising mode setting means for setting a first mode wherein the voice signal from said microphone is to be processed or second mode wherein the voice signal from said microphone is not to be processed;

and means for setting a threshold value which is utilized in said first mode on the basis of the voice signal from said microphone when said second mode is set.