Speakerphone self calibration and beam forming

• US 7,826,624 B2
• Filed: 04/18/2005
• Issued: 11/02/2010
• Est. Priority Date: 10/15/2004
• Status: Active Grant

• Current Assignee: Lifesize, Inc. (Enghouse Systems Limited)
• Original Assignee: Lifesize, Inc. (Enghouse Systems Limited)
• Inventors: Oxford, William V.
• Primary Examiner(s): Chin; Vivian
• Assistant Examiner(s): Tran; Con P
• Application Number:
  US11/108,341
• Publication Number:
  US 20060083389A1
• Time in Patent Office: 2,024 Days
• Field of Search: 381/92, 381/91, 381/122, 381/94.2, 381/94.3, 381/94.1, 381/71.1, 381/98, 381/113, 381/95, 381/96, 381/58, 381/59, 379/388.02, 379/388.01, 379/387.01
• US Class Current: 381/92
• CPC Class Codes: H04R 27/00 Public address systems circuits for preventing acoustic reaction H04R3/02; circuits for distributing signals to loudspeakers H04R3/12; monitoring or testing arrangements for public address systems H04R29/007; amplifiers H03F

Abstract

A communication system includes a set of microphones, a speaker, memory and a processor. The processor is configured to operate on input signals from the microphones to obtain a resultant signal representing the output of a virtual microphone which is highly directed in a target direction. The processor also is configured for self calibration. The processor may provide an output signal for transmission from the speaker. The output signal may be a noise signal, or, a portion of a live conversation. The processor captures one or more input signals in response to the output signal transmission uses the output signal and input signals to estimate parameters of the speaker and/or microphone.

Claims

1. A system comprising:

a set of microphones;

memory that stores program instructions;

a processor configured to read and execute the program instructions from the memory, wherein the program instructions, when executed by the processor, cause the processor to;

(a) receive an input signal corresponding to each of the microphones;

(b) transform the input signals into the frequency domain to obtain respective input spectra;

(c) operate on the input spectra with a set of virtual beams to obtain respective beam-formed spectra, wherein each of the virtual beams is associated with a corresponding frequency range and a corresponding subset of the input spectra, wherein each of the virtual beams operates on portions of input spectra of the corresponding subset of input spectra which have been band limited to the corresponding frequency range, wherein the virtual beams include one or more low end beams and one or more high end beams, wherein each of the low end beams is a beam of a corresponding integer order, wherein each of the high end beams is a delay-and-sum beam;

(d) compute a linear combination of the beam-formed spectra to obtain a resultant spectrum; and

(e) inverse transform the resultant spectrum to obtain a resultant signal.

2. The system of claim 1, wherein the program instructions, when executed by the processor, further cause the processor to:

provide the resultant signal to a communication interface for transmission.

3. The system of claim 1, wherein the microphones of said set of microphones are arranged in a circular array.

4. The system of claim 1, wherein the union of the frequency ranges of the virtual beams covers the range of audio frequencies.

5. The system of claim 1, wherein the union of the frequency ranges of the virtual beams covers the range of voice frequencies.

6. The system of claim 1, wherein the one or more low end beams and the one or more high end beams are directed towards a target direction.

7. The system of claim 1, wherein the one or more low end beams include two low end beams of order two.

8. The system of claim 1, wherein the one or more low end beams include three low end beams of order one.

9. The system of claim 1, wherein the one or more low end beams include two low end beams of order three.

10. The system of claim 1, wherein the one or more high end beams include a plurality of high end beams, wherein the frequency ranges corresponding to the one or more low end beams are less than a predetermined frequency, wherein the frequency ranges corresponding to the high end beams are greater than the predetermined frequency, wherein the frequency ranges corresponding to the high end beams form an ordered succession that covers the frequencies from the predetermined frequency up to a maximum frequency.

11. The system of claim 1, wherein an angular passband of each of the high end beams is approximately 360/N degrees, where N is the number of microphones in the set of microphones.

12. A system comprising:

a set of microphones;

memory that stores program instructions;

a processor configured to read and execute the program instructions from the memory, wherein the program instructions, when executed by the processor, cause the processor to;

(a) receive an input signal from each of the microphones;

(b) operate on the input signals with a set of virtual beams to obtain respective beam-formed signals, wherein each of the virtual beams is associated with a corresponding frequency range and a corresponding subset of the input signals, wherein each of the virtual beams operates on versions of the input signals of the corresponding subset of input signals which have been band limited to the corresponding frequency range, wherein the virtual beams include one or more low end beams and one or more high end beams, wherein each of the low end beams is a beam of a corresponding integer order, wherein each of the high end beams is a delay-and-sum beam;

(c) compute a linear combination of the beam-formed signals to obtain a resultant signal.

13. The system of claim 12, wherein the program instructions, when executed by the processor, further cause the processor to:

provide the resultant signal to a communication interface for transmission.

14. The system of claim 12, wherein the microphones of said set of microphones are arranged in a circular array.

15. A method comprising:

(a) receiving, by a processor, an input signal from each microphone in set of microphones;

(b) transforming, by, the processor, the input signals into the frequency domain to obtain respective input spectra;

(c) operating, by the processor, on the input spectra with a set of virtual beams to obtain respective beam-formed spectra, wherein each of the virtual beams is associated with a corresponding frequency range and a corresponding subset of the input spectra, wherein each of the virtual beams operates on portions of input spectra of the corresponding subset of input spectra which have been band limited to the corresponding frequency range, wherein the virtual beams include one or more low end beams and one or more high end beams, wherein each of the low end beams is a beam of a corresponding integer order, wherein each of the high end beams is a delay-and-sum beam;

(d) computing, by the processor, a linear combination of the beam-formed spectra to obtain a resultant spectrum; and

(e) inverse transforming, by the processor, the resultant spectrum to obtain a resultant signal.

16. The method of claim 15 further comprising:

providing, by the processor, the resultant signal to a communication interface for transmission.

17. The method of claim 15, wherein the set of microphones are arranged in a circular array.

18. A method comprising:

(a) receiving, by a processor, an input signal from each microphone in a set of microphones;

(b) operating, by the processor, on the input signals with a set of virtual beams to obtain respective beam-formed signals, wherein each of the virtual beams is associated with a corresponding frequency range and a corresponding subset of the input signals, wherein each of the virtual beams operates on versions of the input signals of the corresponding subset of input signals which have been band limited to the corresponding frequency range, wherein the virtual beams include one or more low end beams and one or more high end beams, wherein each of the low end beams is a beam of a corresponding integer order, wherein each of the high end beams is a delay-and-sum beam; and

(c) computing, by the processor a linear combination of the beam-formed signals to obtain a resultant signal.

19. The method of claim 18 further comprising:

providing, by the processor, the resultant signal to a communication interface for transmission.

20. The method of claim 18, wherein the set of microphones are arranged in a circular array.