LOUDSPEAKER ARRAY DESIGN

• US 20090304211A1
• Filed: 06/04/2008
• Published: 12/10/2009
• Est. Priority Date: 06/04/2008
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Droppo, James G., Acero, Alejandro, Seltzer, Michael L., Tashev, Ivan J.
• Granted Patent: US 8,379,891 B2
• Time in Patent Office: Days
• US Class Current: 381/182
• 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 that can account for speaker manufacturing tolerances, based on desired functional parameters, comprising:

forming a primary objective function, comprising;

forming a speaker output model for output of a plurality of speakers based on a primary design goal; and

forming a speaker tolerance model that accounts for manufacturing tolerances associated with the plurality of speakers;

defining an unconstrained objective function comprising at least one of;

the primary objective function; and

the primary objective function and one or more associated design constraints;

extracting one or more filter weights, comprising applying an optimization algorithm to the unconstrained objective function; and

applying information from the one or more extracted filter weights to a plurality of filters respectively delivering signals to the plurality of speakers.

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

3. The method of claim 2, the optimization algorithm comprising a gradient descent optimization algorithm.

4. The method of claim 3, applying information from the extracted filter weight to the plurality of filters results in a modification of the amplitude and the phase of a signal to be output from the plurality of filters to respective speakers of the speaker array.

5. The method of claim 4, the primary design goal comprising uniform sound levels in a listening area.

6. The method of claim 4, the primary design goal comprising minimum speaker array power consumption.

7. The method of claim 4, the primary design goal comprising directivity of a sound output from the speaker array.

8. The method of claim 7, defining the primary objective function comprising defining a target pattern that provides for areas of higher volume and areas of lower volume for sound output from the speaker array.

9. The method of claim 8, forming the primary objective function comprising:

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

computing a sound field forming equation that describes a modification made by a plurality of filters on the directivity pattern and how modified sound waves output from the speaker array will propagate through space and time; and

computing a directivity ratio taking into account the target pattern as a ratio of an average power in a listening area to a total average power, wherein the average power is the square of the sound field forming equation

10. The method of claim 9, comprising:

calculating an average directivity by applying the loudspeakers tolerances in the directivity ratio; and

estimating a lower limit (or a worst case) of the average directivity.

11. The method of claim 9, the associated design constraints comprising equalized power response and average zero phase shift in a listening area.

12. A speaker array system, comprising:

a plurality of speakers;

a processing unit configured to;

implement an unconstrained optimization procedure to enhance a primary design constraint, the unconstrained optimization procedure comprises modeling a sound output from the plurality of speakers taking into account manufacturing tolerances associated with the plurality of speakers by modeling the manufacturing tolerances according to a probability distribution; and

extract one or more enhanced filter weights from the unconstrained optimization procedure, the enhanced filter weights comprising information to enhance performance of the speaker array system;

a plurality of filters configured to receive input from the processing unit and modify a signal to be output to respective speakers according to the information in the extracted one or more enhanced filter weights.

13. The system of claim 12, the unconstrained optimization procedure utilizing one or more associated design constraints.

14. The system of claim 13, the plurality of filters configured to modify the amplitude and the phase of the signal to be output from the plurality of filters to respective speakers.

15. The system of claim 14, the plurality of speakers comprising one or more different types of speakers.

16. The system of claim 14, the plurality of filters configured to enhance the directivity of the sound output from the plurality of speakers.

17. The system of claim 14, the probability distribution comprising a Gaussian distribution.

18. The system of claim 14, the speaker array system comprising:

a transmission device configured to facilitate communication with other parties; and

a microphone configured to receive a voice communication from a user.

19. The system of claim 18, the speaker array system comprising:

a visual display unit configured to communicate visually with the other parties;

a visual recording device configured to record visual data of the user; and

an input device configured to receive non-verbal input from the user.

20. A method for defining a speaker array processing algorithm that can account for speaker manufacturing tolerances, based on desired functional parameters, comprising:

forming a primary objective function, comprising;

defining a target pattern that provides for areas of higher volume and areas of lower volume for sound output from the speaker array;

forming a speaker output model for output of a plurality of speakers based on a primary design constraint;

forming a speaker tolerance model, comprising a probability distribution that accounts for manufacturing tolerances associated the plurality of speakers;

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

computing a sound field forming equation that describes a modification made by a plurality of filters on the directivity pattern and how a modified sound waves output from the speaker array will propagate through space and time; and

computing a directivity ratio taking into account the target pattern as a ratio of an average power in a listening area to a total average power,

wherein the average power is the square of the sound field forming equation defining an unconstrained objective function, comprising one of;

the primary objective function; and

the primary objective function and one or more associated design constraints;

extracting one or more filter weights, comprising applying an gradient descent optimization algorithm to minimize the unconstrained objective function; and

applying information from the one or more extracted filter weights to a plurality of filters respectively delivering signals to the plurality of speakers resulting in a modification of the amplitude and the phase of a signal to be output from the plurality of filters to respective speakers of the speaker array.