SOUND DISCRIMINATION METHOD AND APPARATUS

• US 20080317260A1
• Filed: 06/21/2007
• Published: 12/25/2008
• Est. Priority Date: 06/21/2007
• Status: Active Grant

• Current Assignee: Bose Corporation
• Original Assignee: Bose Corporation
• Inventors: Short, William R.
• Granted Patent: US 8,767,975 B2
• Time in Patent Office: Days
• US Class Current: 381/92
• CPC Class Codes: G10L 2021/02161 Number of inputs available containing the signal or the noise to be suppressed
• CPC Class Codes: G10L 21/02 Speech enhancement, e.g. noise reduction or echo cancellation reducing echo effects in line transmission systems H04B3/20; echo suppression in hands-free telephones H04M9/08
• CPC Class Codes: H04R 1/406 microphones
• CPC Class Codes: H04R 29/004 for microphones H04R29/007 takes precedence

Abstract

A method of distinguishing sound sources includes the step of transforming data, collected by at least two transducers which each react to a characteristic of an acoustic wave, into signals for each transducer location. The transducers are separated by a distance of less than about 70 mm or greater than about 90 mm. The signals are separated into a plurality of frequency bands for each transducer location. For each band a comparison is made of the relationship of the magnitudes of the signals for the transducer locations with a threshold value. A relative gain change is caused between those frequency bands whose magnitude relationship falls on one side of the threshold value and those frequency bands whose magnitude relationship falls on the other side of the threshold value. As such, sound sources are discriminated from each other based, on their distance from the transducers.

Claims

1. A method of distinguishing sound sources, comprising the steps of:

transforming data, collected by at least two transducers which each react to a characteristic of an acoustic wave, into signals for each transducer location, the transducers being separated by a distance of less than about 70 mm or greater than about 90 mm;

separating the signals into a plurality of frequency bands for each transducer location;

for each band comparing a relationship of the magnitudes of the signals for the transducer locations with a first threshold value; and

causing a relative gain change between those frequency bands whose magnitude relationship falls on one side of the threshold, value and those frequency bands whose magnitude relationship falls on the other side of the threshold value, such that sound sources are discriminated, from each other based on their distance from the transducers.

2. The method of claim 1, wherein the separating step includes using a fast Fourier transform to convert the signals from a time domain to a frequency domain.

3. The method of claim 1, wherein the comparing step compares a magnitude of a ratio of the signals.

4. The method of claim 1, wherein, the causing step causes those frequency bands whose magnitude comparison falls on one side of the threshold value to receive a gain of about 1.

5. The method of claim 1, wherein the causing step causes those frequency bands whose magnitude comparison falls on the other side of the threshold value to receive a gain of about 0.

6. The method of claim 5, wherein the causing step causes those frequency bands whose magnitude comparison falls on one side of the threshold value to receive a gain of about 1.

7. The method of claim 1, wherein each transducer is an omni-directional microphone.

8. The method of claim 1, further comprising the step of;

after the causing step converting the frequency bands into output signals.

9. The method of claim 8, further comprising the step of;

using the output signals to drive one or more acoustic drivers to produce sound.

10. The method of claim 1, further comprising the step of:

providing a user-variable threshold value such that a user an adjust a distance sensitivity from the transducers.

11. The method of claim 1, wherein the characteristic is a local sound pressure, its first-order gradient, higher-order gradients, or combinations thereof.

12. The method of claim 1, further comprising the step of:

providing a second threshold value different from the first threshold value, wherein the causing step causes a relative gain change between those frequency bands whose magnitude comparison falls in a first range between the threshold values and those frequency bands whose magnitude comparison falls outside the threshold values.

13. The method of claim 12, further comprising the step of:

providing third and fourth threshold values that define a second range that is different from and does not overlap the first range, wherein the causing step causes a relative gain change between those frequency bands whose magnitude comparison falls in the first or second ranges and those frequency bands whose magnitude comparison falls outside the first and second ranges.

14. The method of claim 1, wherein the transducers are separated by a distance of no less than about 250 microns.

15. The method of claim 1, wherein the transducers are separated by a distance of between about 20 mm to about 50 mm.

16. The method of claim 1, wherein the transducers are separated by a distance of between about 25 mm to about 45 mm.

17. The method, of claim 1, wherein the transducers are separated by a distance of about 35 mm.

18. The method of claim 1, wherein the distance between the transducers is measured from a center of a diaphragm for each transducer.

19. The method of claim 1, wherein the causing step fades the relative gain change between a low gain and a high gain.

20. The method of claim 19, wherein the fade of the relative gain change is done across the first threshold value.

21. The method of claim 19, wherein, the fade of the relative gain change is done across a certain magnitude level for an output signal of one or more of the transducers.

22. The method of claim 1, wherein the causing of a relative gain change is effected by (a) a gain term based on the magnitude relationship and (b) a gain term based on a magnitude of an output signal from one or more of the transducers.

23. The method of claim 1, wherein a group of gain terms derived for a first group of frequency bands is also applied to a second group of frequency bands.

24. The method of claim 23, wherein the frequency bands of the first group are lower than the frequency bands of the second group.

25. The method of claim 24, wherein the group of gain terms derived for the first group of frequency bands is also applied to a third group of frequency bands.

26. The method of claim 25, wherein the frequency bands of the first group are lower than the frequency bands of the third group.

27. The method of claim 26, wherein the frequency bands of the first group are lower than the frequency bands of the second group.

28. The method of claim 1, wherein the acoustic wave is traveling in a compressible fluid.

29. The method of claim 28, wherein the compressible fluid is air.

30. The method of claim 1, wherein the acoustic wave is traveling in a substantially incompressible fluid.

31. The method of claim 30, wherein the substantially incompressible fluid is water.

32. The method of claim 1, wherein the causing step causes a relative gain change to the signals from only one of the two transducers.

33. The method of claim 1, wherein for a particular frequency band there is a limit in how quickly a gain for that frequency band can change.

34. The method of claim 33, wherein there is a first, limit for how quickly the gain can increase and a second limit for how quickly the gain can decrease, the first limit and second limit being different.

81. The method of claim 1, wherein a group of gain terms derived for a first octave is also applied to a second octave.

82. The method of claim 81, wherein the first octave is lower than the second octave.

83. The method of claim 81, wherein the group of gain terms derived for the first octave is also applied to a third octave.

84. The method of claim 83, wherein the frequency bands of the first octave is lower than the third octave.

85. The method of claim 84, wherein the frequency bands of the first group are lower than the frequency bands of the second group.

88. The method of claim 83, wherein the characteristics include a time delay between when an acoustic wave is detected by a first transducer and when this wave is defected by a second transducer, whereby an angle to the transducers of a sound source providing energy to a particular band is indicated.

89. The method of claim 8, wherein the output signals are (a) recorded on a storage medium, (b) communicated by a transmitter, and/or (c) further processed and used to present information on location of sound sources.

35. A method of discriminating between sound sources, comprising the steps of:

transforming data, collected by transducers which react to a characteristic of an acoustic wave, into signals for each transducer location;

separating the signals into a plurality of frequency bands for each location;

for each band determining a relationship of the magnitudes of the signals for the locations;

for each band determining from the signals a time delay between when an acoustic wave is detected by a first transducer and when this wave is detected by a second transducer; and

causing a relative gain change between those frequency bands whose magnitude relationship and time delay fall on one side of respective threshold values for magnitude relationship and time delay, and those frequency bands whose (a) magnitude relationship falls on the other side of its threshold value, (b) rime delay falls on the other side of its threshold value, or (c) magnitude relationship and time delay both fall on the other side of their respective threshold values.

36. The method of claim 35, further comprising the step of;

providing an adjustable threshold value for the magnitude relationship.

37. The method of claim 35, further comprising the step of;

providing an adjustable threshold value for the time delay.

38. The method of claim 37, further comprising the step of;

providing an adjustable threshold value for the magnitude relationship.

39. The method of claim 35, wherein the causing step fades the relative gain change between a low gain and a high gain.

40. The method of claim 39, wherein the fade of the relative gain change is done across the magnitude relationship threshold.

41. The method of claim 39, wherein the fade of the relative gain change is done across the time delay threshold.

42. The method of claim 39, wherein the fade of the relative gain change is done across a certain magnitude level for an output signal of one or more of the transducers.

43. The method of claim 35, wherein the causing of a relative gain change is effected by (a) a gain term based on the magnitude relationship and (b) a gain term based on the time delay.

44. The method of claim 43, wherein the causing of a relative gain change is further effected by a gain term based on a magnitude of an output signal from one or more of the transducers.

45. The method of claim 35, wherein a group of gain terms derived, for a first group of frequency bands is also applied to a second group of frequency bands.

46. The method of claim 35, wherein the frequency bands of the first group are lower than the frequency bands of the second group.

47. The method of claim 45, wherein the group of gain terms derived for the first group of frequency bands is also applied to a third group of frequency bands.

48. The method of claim 47, wherein the frequency bands of the first group are lower than the frequency bands of the third group.

49. The method of claim 48, wherein the frequency bands of the first group are lower than the frequency bans of the second group.

50. The method of claim 35, wherein for each frequency band there is an assigned threshold value for magnitude relationship and an assigned threshold value for time delay.

51. A method of distinguishing sound sources, comprising the steps of:

capturing data collected by at least three omni-directional microphones which each react to a characteristic of an acoustic wave;

processing said data to determine (a) which data represents one or more sound sources located less than a certain distance from the microphones, and (b) which data represents one or more sound sources located more than the certain distance from the microphones; and

utilising the results of the processing step to provide a greater emphasis of data representing the sound source(s) in one of (a) or (b) above over data representing the sound source(s) in the other of (a) or (b) above, such that sound sources are discriminated from each other based on their distance from the microphones.

52. The method of claim 51, wherein the certain distance is measured from one of the microphones.

53. The method of claim 51, wherein the utilizing step provides a greater emphasis of data representing the sound source(s) in (a) over data representing the sound source is) in (b).

54. The method of claim 51, further comprising the step of;

after the utilizing step converting the data into output signals.

55. The method of claim 54, further comprising the step of;

using the output signals to drive one or more acoustic drivers to produce sound.

56. The method of claim 51, wherein the characteristic is a local sound pressure, its first-order gradient, higher-order gradients, or combinations thereof.

57. The method of claim 51, wherein a first microphone is a first distance from a second microphone and a second distance from, a third microphone, the first distance being less than the second distance.

58. The device of claim 57, wherein the processing step selects high frequencies from the second microphone and low frequencies from the third microphone which are lower than the high frequencies.

59. The device of claim 58, wherein the low frequencies and high frequencies are combined in the processing step.

60. The device of claim 57, wherein the processing step determines (a) a phase relationship from the data from microphones one and two, and (b) determines a magnitude relationship from the data from, microphones one and three.

90. The method of claim 51, further including the step of:

processing said data to determine (c) which data represents one or more sound sources located less than a certain angle from the microphones, and (d) which data represents one or more sound sources located more than the certain angle from the microphones, the utilizing step being modified to provide a greater emphasis of data representing the sound source(s) in one of (a) or (b) and in one of (c) or (d) over data representing the sound source(s) in the other of (a) or (b) or in the other of (c) or (d), such that sound sources are discriminated from each other based on their distance and angle from the microphones.

98. The method of claim 51, wherein two of the microphones can be connected by an imaginary straight line that extends in either direction to infinity, the third microphone being located away from this line.

61. A personal communication device, comprising:

two transducers which react to a characteristic of an acoustic wave to capture data representative of the characteristic, the transducers being separated by a distance of about 70 mm or less; and

a signal processor for processing said data to determine (a) which data represents one or more sound sources located less than a certain distance from the transducers, and (b) which data represents one or more sound sources located more than the certain distance from the transducers, the signal processor providing a greater emphasis of data representing the sound source(s) in one of (a) or (b) above over data representing the sound source(s) in the other of (a) or (b) above, such that sound sources are discriminated from each other based on their distance from the transducers.

62. The device of claim 61, wherein the signal processor provides a greater emphasis of data representing the sound source(s) in (a) over data representing the sound source(s) in (b).

63. The device of claim 61, wherein the signal processor converts the data into output signals.

64. The device of claim 63, wherein the output signals are used to drive a second acoustic driver remote from the device to produce sound remote from the device.

65. The device of claim 61, wherein the characteristic is a local sound pressure, its first-order gradient, higher-order gradients, or combinations thereof.

66. The device of claim 61, wherein the transducers are separated by a distance of no less than about 250 microns.

67. The device of claim 61, wherein the transducers are separated by a distance of between about 20 mm to about 50 mm.

68. The device of claim 61, wherein the transducers are separated by a distance of between about 25 mm to about 45 mm.

69. The device of claim 61, wherein the transducers are separated by a distance of about 35 mm.

70. The device of claim 61, wherein the distance between the transducers is measured from a center of a diaphragm, for each transducer.

71. The device of claim 61, wherein the device is a cell phone.

72. The device of claim 61, wherein the device is a speaker phone.

91. The method of claim 61, wherein the signal processor also processes the data to determine (c) which data represents one or more sound sources located less than a certain angle from the transducers, and (d) which data represents one or more sound sources located more than the certain angle from the transducers, the signal processor providing a greater emphasis of data representing the sound source(s) in one of (a) or (b) and in one of (c) or (d) over data representing the sound source(s) in the other of (a) or (b) and/or in the other of (o) or (d), such that sound sources are discriminated from each other based on their distance and angle from the transducers.

73. A microphone system, comprising:

a silicon chip;

two transducers secured to the chip which react to a characteristic of an acoustic wave to capture data representative of the characteristic, the transducers being separated by a distance of about 70 mm or less; and

a signal processor secured to the chip for processing said data to determine (a) which data represents one or more sound sources located less than a certain distance from the transducers, and (b) which data represents one or more sound sources located more than the certain distance from the transducers, the signal processor providing a greater emphasis of data representing the sound source(s) in one of (a) or (b) above over data representing the sound source(s) in the other of (a) or (b) above, such that sound sources are discriminated from each other based on their distance from the transducers.

74. The microphone system of claim 73, wherein the transducers are separated by a distance of at least about 250 microns.

75. A method of discriminating between sound sources, comprising the steps of:

transforming data, collected by transducers which react to a characteristic of an acoustic wave, into signals for each transducer location;

separating the signals into a plurality of frequency bands for each location;

for each band determining a relationship of the magnitudes of the signals for the locations;

for each band determining from the signals a phase shift which is indicative of when an acoustic wave is detected by a first transducer and when this wave is detected by a second transducer; and

causing a relative gain change between those frequency bands whose magnitude relationship and phase shift fall on one side of respective threshold values for magnitude relationship and phase shift, and those frequency bands whose (a) magnitude relationship falls on the other side of its threshold value, (b) phase shift falls on the other side of its threshold value, or (c) magnitude relationship and phase shift both fall on the other side of their respective threshold values.

76. The method of claim 75, further comprising the step of;

providing an adjustable threshold value for the magnitude relationship.

77. The method of claim 75, further comprising the step of;

providing an adjustable threshold value for the phase shift.

78. The method of claim 76, further comprising the step of;

providing an adjustable threshold value for the magnitude relationship.

79. A method of discriminating between sound sources, comprising the steps of:

transforming data, collected by transducers which react to a characteristic of an acoustic wave, into signals for each transducer location;

separating the signals into a plurality of frequency bands for each, location;

for each band determining a relationship of the magnitudes of the signals for the locations; and

causing a relative gain change between those frequency bands whose magnitude relationship falls on one side of a threshold value, and those frequency bands whose magnitude relationship falls on the other side of the threshold value, the gain change being faded across the threshold value to avoid abrupt gain changes at or near the threshold.

80. The method of claim 79, further comprising the step of:

for each band determining from the signals a time delay between when an acoustic wave is detected by a first transducer and when this wave is detected by a second transducer, the causing step causing a relative gain change between those frequency bands whose magnitude relationship and time delay fall on one side of respective threshold values for magnitude relationship and time delay, and those frequency bands whose (a) magnitude relationship falls on the other side of its threshold value, (b) time delay falls on the other side of its threshold value, or (c) magnitude relationship and time delay both fall on the other side of their respective threshold values, the gain change being faded across the threshold value to avoid abrupt gain changes at or near the threshold.

86. A method of discriminating between sound sources, comprising the steps of:

transforming data, collected by transducers which react to a characteristic of an acoustic wave, into signals for each transducer location;

separating the signals into a plurality of frequency bands for each location;

for each band determining characteristics of the signals which are indicative of a distance and angle to the transducers of a sound source providing energy to a particular band; and

causing a relative gain change between those frequency bands whose signal characteristics indicate that a sound source providing energy to a particular band meets distance and angle requirements, and those frequency bands whose signal characteristics indicate that a sound source providing energy to a particular band (a) does not meet a distance requirement, (b) does not meet an angle requirement, or (c) does not meet distance and angle requirements.

87. The method of claim 86, wherein the characteristics include a phase shift which is indicative of when an acoustic wave is detected by a first transducer and when this wave is detected by a second transducer, whereby an angle to the transducers of a sound source providing energy to a particular band is indicated.

92. A method of distinguishing sound sources, comprising the steps of:

transforming data, collected by four transducers which each react to a characteristic of an acoustic wave, into signals for each transducer location;

separating the signals into a plurality of frequency bands for each transducer location;

for each band comparing a relationship of the magnitudes of the signals for at least two different pairs of the transducers with a threshold value;

determining for each transducer pair whether the magnitude relationship falls on one side or the other side of the threshold value;

utilizing the results of the determining step to decide whether an overall magnitude relationship falls on one side or the other side of the threshold value; and

causing a relative gain change between those frequency bands whose overall magnitude relationship falls on one side of the threshold value and those frequency bands whose overall magnitude relationship falls on the other side of the threshold value, such that sound sources are discriminated from each other based on their distance from the transducers.

93. The method of claim 92, wherein the four transducers are arranged in a linear array.

94. The method of claim 92, wherein a distance between each adjacent pair of transducers is substantially the same.

95. The method of claim 92, wherein each of the four transducers is located at respective vertices of an imaginary polygon.

96. The method of claim 92, further comprising the step of giving a weight to results of the determining step for each transducer pair.

99. The method of claim 92, wherein the comparing step compares a relationship of the magnitudes of the signals for six unique pairs of the transducers with a threshold value.

97. A method of distinguishing sound sources, comprising the steps of:

switching a sound distinguishing system to a training mode;

moving a sound source to a plurality of locations within a sound, source accept region such that the sound distinguishing system can determine a plurality of thresholds for a plurality of frequency bins;

switching the sound distinguishing system to an operating mode, whereby the sound, distinguishing system will use the thresholds to provide a relative emphasis to sound sources located in the sound source accept region over sound sources located outside the sound source accept region.