Handsfree system for use in a vehicle

• US 20070127736A1
• Filed: 06/30/2004
• Published: 06/07/2007
• Est. Priority Date: 06/30/2003
• Status: Active Grant

• Current Assignee: Cerence Operating Company (Cerence Inc.)
• Original Assignee: Nuance Communications, Inc. (Microsoft Corporation)
• Inventors: Christoph, Markus
• Granted Patent: US 7,826,623 B2
• Time in Patent Office: Days
• 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 2201/403 Linear arrays of transducers
• CPC Class Codes: H04R 2201/405 Non-uniform arrays of transducers or a plurality of uniform arrays with different transducer spacing
• CPC Class Codes: H04R 2430/23 Direction finding using a sum-delay beam-former
• CPC Class Codes: H04R 2430/25 Array processing for suppression of unwanted side-lobes in directivity characteristics, e.g. a blocking matrix
• CPC Class Codes: H04R 2499/13 Acoustic transducers and sound field adaptation in vehicles
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

The invention is directed to a handsfree system for use in a vehicle comprising a microphone array with at least two microphones and a signal processing means wherein the signal processing means comprises the superdirective beamformer with fixed superdirective filters.

Claims

1. Handsfree system for use in a vehicle comprising a microphone array with at

least two microphones and a signal processing means characterized in that

the signal processing means comprises a superdirective beamformer with fixed superdirective filters.

2. Handsfree system according to claim 1 where the beamformer is a regularized superdirective beamformer using a finite regularization parameter p.

3. Handsfree system according to claim 2 where the finite regularization parameter p comprises a finite regularization parameter p depending on the frequency.

4. Handsfree system according to claim 1 where each superdirective filter results from an iterative design based on a predetermined maximum susceptibility.

5. Handsfree system according to claim 1 where each superdirective filter comprises a filter in the time domain.

6. Handsfree system according to claim 1 where the signal processing means further comprises at least one inverse filter for adjusting a microphone transfer function.

7. Handsfree system according to claim 6 where the at least one inverse filter comprises a warped inverse filter.

8. Handsfree system according to claim 6 where each inverse filter comprises an approximate inverse of a non-minimum phase filter.

9. Handsfree system according to claim 6 where each inverse filter is combined with a superdirective filter of the beamformer.

10. Handsfree system according to claim 1 where the beamformer comprises the structure of a generalized sidelobe canceller (GSC).

11. Handsfree system according to claim 1 where the beamformer comprises a minimum variance distortionless response (MVDR) beamformer.

12. Handsfree system according to claim 1 where the microphone array comprises at least two microphones arranged in an endfire orientation with respect to a first position.

13. Handsfree system according to claim 12 where the microphone array comprises at least two microphones arranged in endfire orientation with respect to a second position.

15. Handsfree system according to claim 13 where the at least two microphones in the first endfire orientation and the at least two microphones in the second endfire orientation comprise a microphone in common.

16. Handsfree system according to claim 1 where the microphone array comprises at least two subarrays.

17. Handsfree system according to claim 16 where at least two subarrays comprise at least one microphone in common.

18. Handsfree system according to claim 1 further comprising a frame where each microphone of the microphone array is arranged in a predetermined, position in or on the frame.

19. Handsfree system according to claim 18 where the predetermined position comprises a fixed position in or on the frame.

20. Handsfree system according to claim 1 where at least one microphone comprises a directional microphone.

21. Handsfree system according to claim 20 where the directional microphone comprises a directional microphone with a cardioid characteristic.

22. Handsfree system according to claim 20 where the directional microphone comprises a differential microphone.

23. Handsfree system according to claim 1 comprising a vehicle coupled to the microphone and the beamformer.