Loudspeaker array design

• US 8,379,891 B2
• Filed: 06/04/2008
• Issued: 02/19/2013
• Est. Priority Date: 06/04/2008
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Tashev, Ivan J., Droppo, James G., Seltzer, Michael L., Acero, Alejandro
• Primary Examiner(s): Phan, Hai
• Application Number:
  US12/132,624
• Publication Number:
  US 20090304211A1
• Time in Patent Office: 1,721 Days
• Field of Search: 381/303, 381/300, 381/306, 381/97, 381/98, 381/102, 381/17, 381/305, 381/304
• US Class Current: 381/303
• CPC Class Codes: H04R 2203/12 Beamforming aspects for stereophonic sound reproduction with loudspeaker arrays
• CPC Class Codes: H04R 3/12 for distributing signals to two or more loudspeakers specially adapted for hearing aids H04R25/407

Abstract

Sound signals to be output from a loudspeaker array are modified by a plurality of filters designed according to an unconstrained optimization procedure to improve overall performance (e.g., power, directivity) of the loudspeaker array. More particularly, respective filters are configured to receive a signal to be output to a plurality of loudspeakers. Upon receiving the signal, the respective filters individually modify the received signal according to the results of the unconstrained optimization procedure and then output the individually modified signals to respective loudspeakers. The unconstrained optimization procedure takes into account manufacturing tolerances and individually enhances the signal output to each of a plurality of individual loudspeakers within an array to achieve an overall improvement in performance. In one example, a speaker system utilizes the unconstrained optimization procedure to enable a user to hear an output sound clearly, while adjacent people experience the output sound at lower volume, if at all.

Claims

1. A method for defining a speaker array processing algorithm, comprising:

forming a primary objective function comprising;

defining a target pattern that provides for high area volumes and low area volumes from a speaker array;

forming a directivity pattern by combining a speaker output model and a speaker tolerance model;

computing a sound field forming equation describing a modification made by one or more filters on the directivity pattern and modified sound wave output propagation data; and

computing a directivity ratio based upon the target pattern as a ratio of an average power in a listening area to a total average power, the total average power defined as a square of the sound field forming equation;

defining an unconstrained objective function based upon at least one of the primary objective function and one or more design constraints;

applying an algorithm to the unconstrained objective function to extract one or more filter weights; and

applying the one or more filter weights to one or more filters associated with the speaker array.

2. The method of claim 1, comprising:

calculating an average directivity based upon one or more loudspeaker tolerances specified within the directivity ratio; and

estimating a limit for the average directivity.

3. The method of claim 1, the one or more design constraints comprising an average zero phase shift in the listening area.

4. The method of claim 1, the speaker tolerance model comprising a Gaussian distribution.

5. The method of claim 1, the algorithm comprising a gradient descent algorithm.

6. The method of claim 1, the applying the one or more filter weights comprising:

configuring the one or more filters to output a signal comprising at least one of a modified amplitude and a modified phase to the speaker array.

7. The method of claim 1, the one or more design constraints comprising an equalized power response.

8. A system for defining a speaker array processing algorithm, comprising:

one or more processing units; and

memory comprising instructions that when executed by at least some of the one or more processing units, perform a method comprising;

forming a primary objective function comprising;

defining a target pattern that provides for high area volumes and low area volumes from a speaker array;

forming a directivity pattern by combining a speaker output model and a speaker tolerance model;

computing a sound field forming equation describing a modification made by one or more filters on the directivity pattern and modified sound wave output propagation data; and

computing a directivity ratio based upon the target pattern as a ratio of an average power in a listening area to a total average power, the total average power defined as a square of the sound field forming equation;

defining an unconstrained objective function based upon at least one of the primary objective function and one or more design constraints;

applying an algorithm to the unconstrained objective function to extract one or more filter weights; and

applying the one or more filter weights to one or more filters associated with the speaker array.

9. The system of claim 8, the method comprising

calculating an average directivity based upon one or more loudspeaker tolerances specified within the directivity ratio;

and

estimating a limit for the average directivity.

10. The system of claim 8, the one or more design constraints comprising an average zero phase shift in the listening area.

11. The system of claim 8, the speaker tolerance model comprising a Gaussian distribution.

12. The system of claim 8, the algorithm comprising a gradient descent algorithm.

13. The system of claim 8, the method comprising:

configuring the one or more filters to output a signal comprising at least one of a modified amplitude and a modified phase to the speaker array.

14. The system of claim 8, the one or more design constraints comprising an equalized power response.

15. A tangible computer-readable storage device comprising processor-executable instructions that when executed perform a method for defining a speaker array processing algorithm, comprising:

forming a primary objective function comprising;

defining a target pattern that provides for high area volumes and low area volumes from a speaker array;

forming a directivity pattern by combining a speaker output model and a speaker tolerance model;

computing a sound field forming equation describing a modification made by one or more filters on the directivity pattern and modified sound wave output propagation data; and

computing a directivity ratio based upon the target pattern as a ratio of an average power in a listening area to a total average power, the total average power defined as a square of the sound field forming equation;

defining an unconstrained objective function based upon at least one of the primary objective function and one or more design constraints;

applying an algorithm to the unconstrained objective function to extract one or more filter weights; and

applying the one or more filter weights to one or more filters associated with the speaker array.

16. The tangible computer-readable storage device of claim 15, comprising:

calculating an average directivity based upon one or more loudspeaker tolerances specified within the directivity ratio; and

estimating a limit for the average directivity.

17. The tangible computer-readable storage device of claim 15, the one or more design constraints comprising an average zero phase shift in the listening area.

18. The tangible computer-readable storage device of claim 15, the algorithm comprising a gradient descent algorithm.

19. The tangible computer-readable storage device of claim 15, the applying the one or more filter weights comprising:

configuring the one or more filters to output a signal comprising at least one of a modified amplitude and a modified phase to the speaker array.

20. The tangible computer-readable storage device of claim 15, the one or more design constraints comprising an equalized power response.