Multi-channel loudspeaker matching using variable directivity

• US 9,900,723 B1
• Filed: 06/09/2014
• Issued: 02/20/2018
• Est. Priority Date: 05/28/2014
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Choisel, Sylvain J., Family, Afrooz, Johnson, Martin E., Holman, Tomlinson M.
• Primary Examiner(s): Gay, Sonia
• Application Number:
  US14/300,120
• Time in Patent Office: 1,352 Days
• CPC Class Codes: H04S 7/302 Electronic adaptation of stereophonic sound system to listener position or orientation H04S7/301 takes precedence
• CPC Class Codes: H04S 7/305 Electronic adaptation of stereophonic audio signals to reverberation of the listening space H04S7/301 takes precedence

Abstract

An audio system that maintains an identical or similar direct-to-reverberant ratio for sound produced from a first speaker array and sound produced by a second speaker array at the location of a listener is described. The audio system may determine characteristics of the first and second speaker arrays, including the distance between the first speaker array and the listener and the second speaker array and the listener. Based on these characteristics, beam patterns are selected for one or more of the speaker arrays such that sound produced by each of the speaker arrays maintains a preferred direct-to-reverberant ratio at the location of the listener.

Claims

1. A method for driving a set of speaker arrays to maintain a preferred direct-to-reverberant ratio for sound emitted by each speaker array at a location of a listener, comprising:

determining, by a programmed processor of an electronic audio source, characteristics for a first speaker array and a second speaker array;

determining, by the programmed processor of the electronic audio source, a preferred direct-to-reverberant ratio for sound emitted by the first speaker array and the second speaker array; and

selecting, by the programmed processor of the electronic audio source, a first beam pattern for the first speaker array based on the characteristics of the first speaker array wherein the first speaker array produces the preferred direct-to-reverberant ratio at the location of a listener, and the second speaker array produces the preferred direct-to-reverberant ratio at the location of the listener.

2. The method of claim 1, further comprising:

selecting a second beam pattern for the second speaker array based on the characteristics for the second speaker array such that sound produced by the second speaker array produces the preferred direct-to-reverberant ratio at the location of the listener where the preferred direct-to-reverberant ratio is within 10% from a predefined direct-to-reverberant ratio.

3. The method of claim 1, wherein the preferred direct-to-reverberant ratio is within 10% from the direct-to-reverberant ratio generated by the second speaker array at the location of the listener prior to selecting the first beam pattern.

4. The method of claim 2, wherein determining characteristics for the first speaker array and the second speaker array comprises:

determining a reverberation time of a listening area in which the first and second speaker arrays are located;

determining a distance between the first speaker array and the location of the listener; and

determining a distance between the second speaker array and the location of the listener.

5. The method of claim 4, further comprising:

retrieving a set of calculated direct-to-reverberant ratios and corresponding distances at which these calculated direct-to-reverberant ratios are achieved using a plurality of test beam patterns, wherein the set of calculated direct-to-reverberant ratios are associated with the reverberation time of the listening area,

wherein the first and second beam patterns are selected from the plurality of test beam patterns, based on the preferred direct-to-reverberant ratio and based on the determined distances between the first and second speaker arrays and the location of the listener.

6. The method of claim 1, wherein determining characteristics for the first speaker array and the second speaker array comprises:

driving each of the first speaker array and the second speaker array to sequentially output sound using a plurality of test beam patterns;

detecting, by a listening device, test sounds generated by each speaker array-beam pattern combination, of the first and second speaker arrays and the plurality of test beam patterns; and

determining a test direct-to-reverberant ratio for each said combination, based on the detected sounds.

7. The method of claim 6, further comprising:

determining a first test direct-to-reverberant ratio associated with the first speaker array that is identical to or within a prescribed threshold from a second test direct-to-reverberant ratio associated with the second speaker array, wherein the selected first beam pattern is the beam pattern that generated the first test direct-to-reverberant ratio, and the beam pattern that generated the second test direct-to-reverberant ratio is selected for the second speaker array.

8. The method of claim 2, further comprising:

selecting a gain value to apply to the first speaker array, wherein the gain value allows the level of sound produced by each of the first and second speaker arrays to be identical at the location of the listener;

driving the first speaker array using

     1) the first beam pattern, and

     2) the gain value to produce the preferred direct-to-reverberant ratio and a preferred sound level at the location of the listener; and

driving the second speaker array using the second beam pattern to produce the preferred direct-to-reverberant ratio and the preferred sound level at the location of the listener.

9. The method of claim 2, wherein the first beam pattern and the second beam pattern are one or more of an omnidirectional beam pattern, a cardioid beam pattern, a second order beam pattern, and a fourth order beam pattern.

10. A computing device for driving a set of speaker arrays to maintain a preferred direct-to-reverberant ratio for sound emitted by each speaker array at a location of a listener, comprising:

a hardware processor; and

a non-transitory memory unit for storing instructions, which when executed by the hardware processor;

determine characteristics for a first speaker array and a second speaker array;

determine a preferred direct-to-reverberant ratio for sound emitted by the first speaker array and the second speaker array; and

select a first beam pattern for the first speaker array based on the characteristics for the first speaker array wherein the first speaker array produces the preferred direct-to-reverberant ratio at the location of a listener, and the second speaker array produces the preferred direct-to-reverberant ratio at the location of the listener.

11. The computing device of claim 10, wherein the memory unit includes further instructions which when executed by the hardware processor:

select a second beam pattern for the second speaker array based on the characteristics for the second speaker array such that sound produced by the second speaker array produces the preferred direct-to-reverberant ratio at the location of the listener where the preferred directo-to-reverberant ratio is within 25% from a predefined direct-to-reverberant ratio.

12. The computing device of claim 10, wherein the preferred direct-to-reverberant ratio is within 25% from the direct-to-reverberant ratio generated by the second speaker array at the location of the listener prior to selecting the first beam pattern.

13. The computing device of claim 11, wherein the memory unit includes further instructions which when executed by the hardware processor:

determine a reverberation time of a listening area in which the first and second speaker arrays are located;

determine a distance between the first speaker array and the location of the listener; and

determine a distance between the second speaker array and the location of the listener.

14. The computing device of claim 13, wherein the memory unit includes further instructions which when executed by the hardware processor:

retrieve a set of calculated direct-to-reverberant ratios and corresponding distances at which these calculated direct-to-reverberant ratios are achieved using a plurality of test beam patterns, wherein the set of calculated direct-to-reverberant ratios are associated with the reverberation time of the listening area,

wherein the first and second beam patterns are selected from the plurality of test beam patterns, based on the preferred direct-to-reverberant ratio and based on the determined distances between the first and second speaker arrays and the location of the listener.

15. The computing device of claim 10, wherein the memory unit includes further instructions which when executed by the hardware processor:

drive each of the first speaker array and the second speaker array to sequentially output sound using a plurality of test beam patterns;

detect, by a listening device, test sounds generated by each speaker array-beam pattern combination of the first and second speaker arrays and the plurality of test beam patterns; and

determine a test direct-to-reverberant ratio for each said based on the detected sounds.

16. The computing device of claim 15, wherein the memory unit includes further instructions which when executed by the hardware processor:

determine a first test direct-to-reverberant ratio associated with the first speaker array that is identical to or within a prescribed threshold from a second test direct-to-reverberant ratio associated with the second speaker array, wherein the selected first beam pattern is the beam pattern that generated the first test direct-to-reverberant ratio, and the beam pattern that generated the second test direct-to-reverberant ratio is selected for the second speaker array.

17. The computing device of claim 11, wherein the memory unit includes further instructions which when executed by the hardware processor:

select a gain value to apply to the first speaker array, wherein the gain value allows the level of sound produced by each of the first and second speaker arrays to be identical at the location of the listener;

drive the first speaker array using

     1) the first beam pattern, and

     2) the gain value to produce the preferred direct-to-reverberant ratio and a preferred sound level at the location of the listener; and

drive the second speaker array using the second beam pattern to produce the preferred direct-to-reverberant ratio and the preferred sound level at the location of the listener.

18. The computing device of claim 16, wherein the first and second speaker arrays are integrated within the computing device.

19. An article of manufacture for driving a set of speaker arrays to maintain a preferred direct-to-reverberant ratio for sound emitted by each speaker array at the location of a listener, comprising:

a non-transitory machine-readable storage medium that stores instructions which, when executed by a processor in a computer,

determine characteristics for a first speaker array and a second speaker array;

determine a preferred direct-to-reverberant ratio for sound emitted by the first speaker array and the second speaker array; and

select a first beam pattern for the first speaker array based on the characteristics for the first speaker array wherein the first speaker array produces the preferred direct-to-reverberant ratio at the location of a listener, and the second speaker array produces the preferred direct-to-reverberant ratio at the location of the listener.

20. The article of manufacture of claim 19, wherein the non-transitory machine-readable storage medium stores further instructions which, when executed by the processor:

select a second beam pattern for the second speaker array based on the characteristics for the second speaker array such that sound produced by the second speaker array produces the preferred direct-to-reverberant ratio at the location of the listener.

21. The article of manufacture of claim 19, wherein the preferred direct-to-reverberant ratio is within 15% from the direct-to-reverberant ratio generated by the second speaker array at the location of the listener prior to selecting the first beam pattern.

22. The article of manufacture of claim 20, wherein the non-transitory machine-readable storage medium stores further instructions which, when executed by the processor:

determine a reverberation time of a listening area in which the first and second speaker arrays are located;

determine a distance between the first speaker array and the location of the listener; and

determine a distance between the second speaker array and the location of the listener.

23. The article of manufacture of claim 22, wherein the non-transitory machine-readable storage medium stores further instructions which, when executed by the processor:

retrieve a set of calculated direct-to-reverberant ratios and corresponding distances at which these calculated direct-to-reverberant ratios are achieved using a plurality of test beam patterns, wherein the set of calculated direct-to-reverberant ratios are associated with the reverberation time of the listening area,

wherein the first and second beam patterns are selected from the plurality of test beam patterns, based on the preferred direct-to-reverberant ratio and the determined distances between the first and second speaker arrays and the location of the listener.

24. The article of manufacture of claim 19, wherein the non-transitory machine-readable storage medium stores further instructions which, when executed by the processor:

drive each of the first speaker array and the second speaker array to sequentially output sound using a plurality of test beam patterns;

detect, by a listening device, test sounds generated by each combination of the first and second speaker arrays and the plurality of test beam patterns; and

determine a test direct-to-reverberant ratio for each combination of

     1) the first and second speaker arrays and

     2) the plurality of test beam patterns based on the detected sounds.

25. The article of manufacture of claim 24, wherein the non-transitory machine-readable storage medium stores further instructions which, when executed by the processor:

determine a first test direct-to-reverberant ratio associated with the first speaker array that is identical to or within a prescribed threshold from a second test direct-to-reverberant ratio associated with the second speaker array, wherein the preferred direct-to-reverberant ratio is set based on the first test direct-to-reverberant ratio.

26. The article of manufacture of claim 25, wherein the selected first beam pattern is the beam pattern that generated the first test direct-to-reverberant ratio and the beam pattern that generated the second test direct-to-reverberant ratio is selected for the second speaker array.

27. The article of manufacture of claim 19, wherein the non-transitory machine-readable storage medium stores further instructions which, when we executed by the processor are such that

the preferred direct-to-reverberant ratio is within 15% from a predefined direct-to-reverberant ratio.