Cluster of first-order microphones and method of operation for stereo input of videoconferencing system

• US 20070147634A1
• Filed: 12/27/2005
• Published: 06/28/2007
• Est. Priority Date: 12/27/2005
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Polycom Incorporated (HP Inc.)
• Inventors: Chu, Peter
• Granted Patent: US 8,130,977 B2
• Time in Patent Office: Days
• US Class Current: 381/92
• CPC Class Codes: H04R 1/406 microphones
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

An arbitrarily positioned cluster of three microphones can be used for stereo input of a videoconferencing system. To produce stereo input, right and left weightings for signal inputs from each of the microphones are determined. The right and left weightings correspond to preferred directive patterns for stereo input of the system. The determined right weightings are applied to the signal inputs from each of the microphones, and the weighted inputs are summed to product the right input. The same is done for the left input using the determined left weightings. The three microphones are preferably first-order, cardioid microphone capsules spaced close together in an audio unit, where each faces radially outward at 120-degrees. The orientation of the arbitrarily positioned cluster relative to the system can be determined by directly detecting the orientation or by using stored arrangements.

Claims

1. A method of operating a cluster of at least three microphones for at least two channel inputs of an audio system, each of the microphones being an N^th-order microphone where N≧

1, the cluster being positionable in an arbitrary orientation relative to the audio system, the method comprising;

determining first weightings to be applied to signal input generated by each microphone, the first weightings corresponding to the arbitrary orientation of the microphones relative to a first of the at least two channel inputs of the audio system;

determining second weightings to be applied to signal input generated by each microphone, the second weightings corresponding to the arbitrary orientation of the microphones relative to a second of the at least two channel inputs of the audio system;

producing first channel input for the audio system by;

weighting signal input generated by each microphone by its corresponding first weighting, and

combining the first weighted signal inputs of the microphones; and

producing second channel input for the audio system by;

weighting signal input generated by each microphone by its corresponding second weighting, and

combining the second weighted signal inputs of the microphones.

2. The method of claim 1, wherein each of the microphones comprises a first-order microphone having a cardioid, a hypercardioid, or a dipole directive pattern.

3. The method of claim 1, wherein the cluster of microphones comprises three microphones positioned substantially on a plane and positioned radially around a center of the cluster at about every 120-degrees from one another.

4. The method of claim 1, wherein the audio system is selected from the group consisting of a videoconferencing system, a multi-channel audio conferencing system, and a recording system.

5. The method of claim 1, wherein the at least two channel input signals for the audio system comprise right and left stereo input signals for the audio system.

6. The method of claim 1, further comprising a conference phone having the cluster of at least three microphones.

7. The method of claim 1, further comprising determining the arbitrary orientation of the cluster of microphones relative to the audio system.

8. The method of claim 7, wherein determining the arbitrary orientation of the cluster of microphones relative to the audio system comprises:

emitting audio with the audio system;

receiving signal input generated by each microphone in response to the emitted audio;

comparing each of the received signal inputs with each other; and

determining the arbitrary orientation of the cluster of microphones from the compared signal inputs.

9. The method of claim 8, wherein comparing each of the received signal inputs with each other comprises comparing differences in magnitudes of the received signal inputs.

10. The method of claim 9, wherein comparing differences in magnitudes of the received signal inputs comprises comparing the differences in magnitudes over a plurality of time intervals.

11. The method of claim 8, wherein comparing each of the received signal inputs with each other comprises comparing differences in arrival times of the received signal inputs.

12. The method of claim 7, wherein determining the arbitrary orientation of the cluster of microphones relative to the audio system comprises:

storing a plurality of stored orientations for the cluster of microphones;

emitting audio with the audio system;

receiving signal input generated by each microphone in response to the emitted audio; and

processing the received signal inputs using each of the stored orientations;

comparing each of the processed signal inputs of the stored orientations with each other; and

selecting one of the stored orientations based on the compared signal inputs.

14. The method of claim 1, further comprising operating a plurality of the audio units for stereo operation in either an endfire or a broadside orientation relative to the audio system.

13. The method of 12, wherein processing the received signal inputs using each of the stored orientations comprises:

weighting the received signal inputs using weightings for each microphone, the weightings associated with each of the stored orientations relative to the at least two channel inputs of the audio system, and

combining the weighted signal inputs for a stored orientation to produce the processed signal input for that stored orientation.

15. An audio system, comprising:

an audio unit comprising at least three microphones, each of the microphones being an N^th-order microphone where N≧

1, the audio unit being arbitrarily oriented with respect to the audio system;

a control unit coupled to the audio unit and configured to determine at least two channel weightings for each microphone as a function of the arbitrary orientation of the audio unit with respect to the audio system, and to generate at least two channel input signals for the audio system by applying the determined channel weightings to signal inputs generated by each microphone.

16. The audio system of claim 15, where the audio system is selected from the group consisting of a videoconferencing system, a multi-channel audio conferencing system, and a recording system.

17. The audio system of claim 15, further comprising a conference phone having the audio unit.

18. The audio system of claim 15, wherein the at least two channel input signals for the audio system comprise right and left stereo input signals for the audio system.

19. The audio system of claim 15, wherein each of the microphones comprises a first-order microphone having a cardioid, a hypercardioid, or a dipole directive pattern.

20. The audio system of claim 15, wherein the audio unit comprises a cluster of three microphones arranged at approximately 120-degrees around a center of the audio unit.

21. The audio system of claim 20, wherein each of the three microphones comprises a microphone capsule being about 5-mm by 10-mm in dimension and being spaced apart approximately 10-mm from center to center of one another.

22. The audio system of claim 15, wherein to generate that at least two channel input signals for the audio system, the control unit is configured to:

weight the signal input generated by each of the microphones by its corresponding channel weightings,

combine the weighted signal inputs of a channel to produce the channel input for the conferencing system for that channel.

23. The audio system of claim 15, wherein to determine the at least two channel weightings for each microphone as a function of the arbitrary orientation of the audio unit, the control unit is operable to automatically determine the arbitrary orientation of the audio unit relative to the audio system.

24. The audio system of claim 23, wherein to automatically determine the arbitrary orientation of the audio unit relative to the audio system, the control unit is operable to:

emit audio with the conferencing system;

receive signal input from each microphone in response to the emitted audio;

compare the received signal inputs with each other; and

determine the arbitrary orientation of the cluster of microphones from the compared signal inputs.

25. The audio system of claim 24, wherein to compare the received signal inputs with each other, the control unit is operable to compare differences in magnitudes between the received signal inputs.

26. The audio system of claim 25, wherein to compare differences in magnitudes between the received signal inputs, the control unit is operable to compare the differences in magnitudes over a plurality of time intervals.

27. The audio system of claim 24, wherein to compare the received signal inputs with each other, the control unit is operable to compare differences in arrival times between the received signal inputs.

28. The audio system of claim 23, wherein to automatically determine the arbitrary orientation of the audio unit relative to the audio system, the control unit is operable to:

store a plurality of stored orientations for the audio unit;

emit audio with the audio system;

receive signal input from each microphone in response to the emitted audio;

process the received signal inputs using each of the stored orientations;

compare each of the processed signal inputs of the stored orientations with each other; and

selecting one of the stored orientations based on the compared signal inputs.

30. The audio system of claim 15, further comprising at least one additional audio unit coupled to the audio unit, wherein the control unit is configured to operate the audio units for stereo operation in either an endfire or a broadside orientation relative to the audio system.

29. The audio system of 28, wherein to process the received signal inputs using each of the stored orientations, the control unit is operable to:

weight the received signal inputs using multi-channel weightings for each microphone, the multi-channel weightings associated with each of the stored orientations relative to the at least two channel inputs of the audio system, and

combine the weighted signal inputs for a stored orientation to produce the processed signal input for that stored orientation.