Sound discrimination method and apparatus

• US 8,767,975 B2
• Filed: 06/21/2007
• Issued: 07/01/2014
• Est. Priority Date: 06/21/2007
• Status: Active Grant

• Current Assignee: Bose Corporation
• Original Assignee: Bose Corporation
• Inventors: Short, William R.
• Primary Examiner(s): Chin, Vivian
• Assistant Examiner(s): Tran, Con P
• Application Number:
  US11/766,622
• Publication Number:
  US 20080317260A1
• Time in Patent Office: 2,567 Days
• Field of Search: 381/92, 381/99, 381/98, 381/91, 381/122, 381/111, 381/56, 708/821, 708/820, 708/801
• 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 a plurality of transducers which each react to a characteristic of an acoustic wave, into a plurality of signals, one for each respective transducer, the transducers being separated by a distance of less than about 70 mm or greater than about 90 mm, the plurality of transducers having a location;

separating each of the plurality of signals into a corresponding plurality of frequency bands;

for each frequency, comparing a magnitude difference of corresponding frequency bands of the plurality of signals to a predetermined first magnitude difference threshold value, the magnitude difference threshold value associated with a predetermined distance from the location of the plurality of the transducers; and

causing, for a first signal of the plurality of signals, a relative gain change for a first set of frequency bands relative to a second set of frequency bands of the corresponding frequency bands of the first signal, the first set of frequency bands including frequency bands where the magnitude difference falls on one side of the magnitude difference threshold value, the second set of frequency bands including frequency bands where the magnitude difference falls on the other side of its the magnitude difference threshold value, such that the 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, further comprising the step of;

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

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

providing a user-variable magnitude difference threshold value such that a user can adjust the distance discrimination from the location of the plurality of transducers.

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

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

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

7. The method of claim 6, further comprising the step of:

providing third and fourth magnitude difference 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 difference comparison falls in the first or second ranges and those frequency bands whose magnitude difference comparison falls outside the first and second ranges.

8. The method of claim 1, wherein a pair of the plurality of the transducers are separated by a distance of no less than about 250 microns, where the separation distance is measured between the centers of diaphragms of the transducers.

9. The method of claim 1, wherein a pair of the plurality of transducers are separated by a distance of between about 20 mm to about 50 mm, where the separation distance is measured between the centers of diaphragms of the transducers.

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

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

12. The method of claim 1, wherein the causing step causes a relative gain change to a composite signal formed as a combination of signals of the plurality of signals.

13. 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.

14. The method of claim 13, 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.

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

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

separating each of the plurality of signals into a corresponding plurality of frequency bands;

for each frequency, comparing a magnitude difference of corresponding frequency bands of the plurality of signals to a predetermined magnitude difference threshold value, the magnitude difference threshold value associated with a predetermined distance from the location of the plurality of the transducers;

for each frequency, comparing a time difference of corresponding frequency bands of the plurality of signals to a predetermined time difference threshold value, where the time difference is the difference in time between when an acoustic wave emitted by a sound source at a distance from the location of the plurality of transducers is detected by a first transducer of the plurality of transducers and when this wave is detected by a second transducer of the plurality of transducers, where the time difference threshold value is associated with a predetermined angle relative to the location of the plurality of transducers; and

causing, for a first signal of the plurality of signals, a relative gain change for a first set of frequency bands relative to a second set of frequency bands of the corresponding frequency bands of the first signal, the first set of frequency bands including frequency bands where the magnitude difference and the time difference fall on one side of respective threshold values for magnitude difference and time difference, the second set of frequency bands including frequency bands where (a) the magnitude difference falls on the other side of the respective magnitude difference threshold value, (b) the time difference falls on the other side of the respective time difference threshold value, or (c) the magnitude difference and time difference both fall on the other side of their respective magnitude difference and time difference threshold values, such that the sound sources are discriminated from each other based on their distance and angle relative to the location of the plurality of transducers.

16. The method of claim 15, further comprising the step of;

providing an adjustable magnitude difference threshold value.

17. The method of claim 15, further comprising the step of;

providing an adjustable time difference threshold value.

18. The method of claim 17, further comprising the step of;

providing an adjustable magnitude difference threshold value.

19. The method of claim 15, wherein the causing step fades the relative gain change between a low gain and a high gain.

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

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

separating each of the plurality of signals into a corresponding plurality of frequency bands;

for each frequency, comparing a magnitude difference of corresponding frequency bands of the plurality of signals to a predetermined magnitude difference threshold value, the magnitude difference threshold value associated with a predetermined distance from the location of the plurality of the transducers;

for each frequency, comparing a phase difference of corresponding frequency bands of the plurality of signals to a predetermined phase difference threshold value, the phase difference threshold value associated with a predetermined angle relative to the location of the plurality of transducers,

causing, for a first signal of the plurality of signals, a relative gain change for a first set of frequency bands relative to a second set of frequency bands of the corresponding frequency bands of the first signal, the first set of frequency bands including frequency bands where the magnitude difference and phase difference fall on one side of respective threshold values for magnitude difference and phase difference, the second set of frequency bands including frequency bands where (a) the magnitude difference falls on the other side of the respective magnitude difference threshold value, (b) the phase difference falls on the other side of the respective phase difference threshold value, or (c) the magnitude difference and phase difference both fall on the other side of their respective magnitude difference and phase difference threshold values, such that the sound sources are discriminated from each other based on their distance and angle relative to the location of the plurality of transducers.

21. The method of claim 20, further comprising the step of;

providing an adjustable magnitude difference threshold value.

22. The method of claim 20, further comprising the step of;

providing an adjustable phase difference threshold value.

23. The method of claim 20, further comprising the step of;

providing an adjustable magnitude difference threshold value.