Directable microphone system

• US 4,485,484 A
• Filed: 10/28/1982
• Issued: 11/27/1984
• Est. Priority Date: 10/28/1982
• Status: Expired due to Term

• Current Assignee: Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Original Assignee: AT&T, Inc.
• Inventors: Flanagan, James L.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/437,290
• Time in Patent Office: 761 Days
• Field of Search: 381/66, 381/92, 381/111, 381/53
• US Class Current: 381/92
• CPC Class Codes: H04R 1/406 microphones
• CPC Class Codes: H04R 2201/401 2D or 3D arrays of transducers
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

A microphone arrangement focuses on a prescribed volume in a large room such as an auditorium. The arrangement includes a plurality of directable beam microphone structures. Each beam is directed to a prescribed location. The signals produced in the microphone structures are selectively adjusted to accept sounds from a predetermined volume surrounding the location and to reject sounds outside the prescribed volume.

Claims

1. A signal processing arrangement for reducing audio interference in a reverberative environment comprising:

a plurality of directable beam forming electroacoustic transducer means;

means for steering the beam of each transducer means to a prescribed location in said environment; and

means responsive to the output signals of said directable beam forming transducer means for forming a signal corresponding to sounds emanating from a predetermined volume surrounding said prescribed location.

2. A signal processing arrangement for reducing audio interference in a reverberative environment according to claim 1 wherein each directable beam forming transducer means comprises:

an array of spaced electroacoustic transducer elements each being adapted to generate a signal corresponding to sound waves incident thereon; and

means responsive to the transducer element signals for generating a signal representative of sound waves within a prescribed beam pattern.

3. A signal processing arrangement for reducing audio interference in a reverberative environment according to claim 2 wherein said means for forming a signal corresponding to sounds emanating from a predetermined volume surrounding said prescribed location comprises means responsive to said prescribed beam pattern representative signals for adjusting the characteristics of each beam pattern representative signal.

4. A signal processing arrangement for reducing audio interference in a reverberative environment according to claim 3 wherein said adjusting means comprises means responsive to each beam pattern representative signal for reducing the phase differences between said beam pattern representative signals.

5. A signal processing arrangement for reducing audio interference in a reverberative environment according to claim 4 wherein said phase difference reducing means comprises means for rendering the phase characteristic of each beam pattern representative signal substantially similar to the phase characteristic of the other beam pattern representative signals.

6. A signal processing arrangement for reducing audio interference in a reverberative environment according to claim 5 wherein said beam pattern representative signal phase characteristic similarity rendering means comprises means for partitioning said beam pattern representative signal into a plurality of frequency bands, means responsive to each frequency band signal for generating a band representative signal having a prescribed phase characteristic, and means responsive to said band representative signals for forming a beam pattern representative signal replica having a predetermined phase characteristic.

7. A signal processing arrangement for reducing audio interference in a reverberative environment according to claim 6 wherein each beam pattern representative replica signal has substantially the same phase characteristic.

8. A signal processor for reducing audio interference in a reverberative environment comprising:

first and second directable beam forming electroacoustic transducer means;

means for directing the beams of the first and second transducer means to a pescribed location in said environment; and

means for selectively adjusting the differences between the output signals of said first and second transducer means to generate a signal representative of sounds emanating from a prescribed volume surrounding said prescribed location.

9. A signal processing arrangement for reducing audio interference in a reverberative environment according to claim 8 wherein each directable beam forming transducer means comprises:

an array of regularly spaced electroacoustic transducer elements each being adapted to generate a signal corresponding to sound waves incident thereon; and

means responsive to the transducer element signals, said transducer element spacing and the number of transducer elements for generating a signal representative of sound waves within a prescribed beam pattern.

10. A signal processing arrangement for reducing audio interference in a reverberative environment according to claim 9 wherein said difference adjusting means comprises:

means responsive to said first transducer means output signal for generating a third signal having a predetermined phase characteristic; and

means responsive to said second transducer means output signal for generating a fourth signal having substantially the same phase characteristic.

11. A signal processing arrangement for reducing audio interference in a reverberative environment according to claim 10 wherein each of said third and fourth signal generating means comprises:

means for partitioning said transducer means output signal into a plurality of frequency bands,

means responsive to each frequency band signal for generating a band representative signal having a prescribed phase characteristic, and

means responsive to said band representative signals for forming a beam pattern representative signal replica having a predetermined phase characteristic.

12. A signal processing arrangement for reducing audio interference in a reverberative environment according to claim 11 wherein said reverberative environment is a room, said first transducer array is located on one wall of said room and said second transducer array is located on an adjacent wall of said room.

13. A method of reducing audio interference in a reverberative environment having a plurality of directable beam electroacoustic transducers each including an array of spaced electroacoustic transducer elements each being adapted to generate a signal corresponding to sound waves incident thereon comprising the steps of:

steering the beam of each directable beam transducer to a prescribed location in said environment; and

forming a signal corresponding to sounds emanating from a predetermined volume surrounding said prescribed location responsive to the output signals of said directable beam transducers.

14. A method for reducing audio interference in a reverberative environment according to claim 13 wherein said signal formation comprises:

generating a signal representative of sound waves within a prescribed beam pattern responsive to the transducer element signals.

15. A method for reducing audio interference in a reverberative environment according to claim 14 wherein forming a signal corresponding to sounds emanating from a predetermined volume surrounding said prescribed location further comprises adjusting the phase characteristics of each beam pattern representative signal responsive to said prescribed beam pattern representative signals.

16. A method for reducing audio interference in a reverberative environment according to claim 15 wherein said phase adjusting step comprises reducing the phase differences between said beam pattern representative signals responsive to each beam pattern representative signal.

17. A method for reducing audio interference in a reverberative environment according to claim 16 wherein said phase difference reducing comprises rendering the phase characteristic of each beam pattern representative signal substantially similar to the phase characteristic of the other beam pattern representative signals.

18. A method for reducing audio interference in a reverberative environment according to claim 17 wherein said beam pattern representative signal phase characteristic similarity rendering comprises partitioning said beam pattern representative signal into a plurality of frequency bands, generating a band representative signal having a prescribed phase characteristic responsive to each frequency band signal, and forming a beam pattern representative signal replica having a predetermined phase characteristic responsive to said band representative signals.

19. A method for reducing audio interference in a reverberative environment according to claim 18 wherein each beam pattern representative replica signal has substantially the same phase characteristic.