Modal based architecture for controlling the directivity of loudspeaker arrays

Patent metadata

Field	Value
Publication number	US-9762999-B1
Application number	US-201514869760-A
Country	US
Kind code	B1
Filing date	Sep 29, 2015
Priority date	Sep 30, 2014
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

A directivity pattern generator for producing sound patterns using a modal architecture is described. The directivity pattern generator may include a beam pattern mixing unit, which defines sound patterns to be emitted by an audio system in terms of a set of frequency invariant modes or modal patterns. The beam pattern mixing unit produces a set of modal gains representing the level or degree each of the predefined modal patterns is to be applied to a set of audio streams. Modal filters may be used to modal amplitudes that compensate for inefficiencies of the each modal pattern at low frequencies. The directivity pattern generator may include a modal decomposition unit for generating driving signals for each transducer in one or more loudspeaker arrays based on weighted values for the modal gains/amplitudes.

First claim

What is claimed is:

1. A method for driving a loudspeaker array, comprising:
sampling one or more audio streams to produce a matrix of one or more audio samples; multiplying the matrix of one or more samples with a beam pattern mixing matrix, which represents a plurality of predefined modal patterns, to produce a modal gain value for each of the plurality of predefined modal patterns; and
multiplying a matrix of the modal gain values with a modal decomposition matrix to produce a drive signal for each of a plurality of transducers in the loudspeaker array such that the loudspeaker array produces a separate output beam pattern for each of the one or more audio streams based on the plurality of predefined modal patterns.

2. The method of claim 1 , wherein the beam pattern mixing matrix is a matrix of real numbers representing weights for the predefined modal patterns to produce the separate output beam pattern for each of the one or more audio streams.

3. The method of claim 1 , wherein the modal decomposition matrix is a matrix of real numbers representing assignment levels for each predefined modal pattern to each transducer in the loudspeaker array such that the transducers in the loudspeaker array produce each of the predefined modal patterns based on weights represented in the beam pattern mixing matrix.

4. The method of claim 1 , wherein the matrix of modal gain values includes individual real number coefficients for each of the predefined modal patterns.

5. The method of claim 1 , further comprising:
filtering each modal gain value in the matrix of modal gain values, using a separate modal filter, wherein each modal filter corresponds to a separate modal pattern in the plurality of predefined modal patterns and each modal filter boosts a power level of a corresponding modal gain value below a roll-off frequency associated with a corresponding modal pattern.

6. The method of claim 5 , wherein the modal gain values are separately filtered by multiple sets of modal filters,
wherein each set of the modal filters includes a modal filter for each combination of 1) the plurality of predefined modal patterns and 2) each ring of transducers in the loudspeaker array,
wherein each set of the modal filters is configured based on a diameter of a ring of transducers within the loudspeaker array controlled by the set of modal filters.

7. The method of claim 1 , further comprising:
filtering the drive signals using a set of vertical control and matching filters, wherein a separate vertical control and matching filter is assigned to each transducer in the loudspeaker array, and each vertical control and matching filter adjusts a corresponding drive signal, to 1) provide vertical control to the output beam patterns and 2) match transducers of different size or type within the loudspeaker array.

8. The method of claim 6 , wherein each set of modal filters further 1) provides vertical control to the output beam patterns and 2) matches transducers of different size or type within the loudspeaker array.

9. The method of claim 1 , wherein the predefined modal patterns include a vertical dipole pattern, a horizontal dipole pattern, and an omnidirectional pattern.

10. A directivity pattern generator, comprising:
a beam pattern mixing unit to generate modal gains for predefined modal patterns by multiplying a matrix of weights corresponding to the predefined modal patterns with a matrix of audio samples for one or more audio streams; and
a modal decomposition unit to generate drive signals corresponding to desired sound patterns by multiplying a matrix of the modal gains with a modal decomposition matrix to produce a drive signal for each of a plurality of transducers in a loudspeaker array such that the loudspeaker array produces a separate desired sound pattern for each of the one or more audio streams based on the predefined modal patterns, wherein the beam pattern mixing unit is coupled to the model decomposition unit.

11. The directivity pattern generator of claim 10 , further comprising:
a sampler for sampling the one or more audio streams to generate the matrix of audio samples.

12. The directivity pattern generator of claim 10 , further comprising:
modal filters to filter each modal gain in the matrix of modal gains using a separate modal filter, wherein each modal filter corresponds to a separate modal pattern in the predefined modal patterns and each modal filter boosts a power level of a corresponding modal gain below a roll-off frequency associated with a corresponding modal pattern.

13. The directivity pattern generator of claim 12 , wherein the modal gains are separately filtered by multiple sets of modal filters,
wherein each set of modal filters includes a modal filter for each combination of 1) the plurality of predefined modal patterns and 2) each ring of transducers in the loudspeaker array,
wherein each set of modal filters is configured based on a diameter of a ring of transducers within the loudspeaker array controlled by the set of modal filters.

14. The directivity pattern generator of claim 10 , further comprising:
a set of vertical control and matching filters to filter the drive signals, wherein a separate vertical control and matching filter is assigned to each transducer in the loudspeaker array, and each vertical control and matching filter adjusts a corresponding drive signal, to 1) provide vertical control to the output beam patterns and 2) match transducers of different size or type within the loudspeaker array.

15. The directivity pattern generator of claim 13 , wherein each set of modal filters further 1) provides vertical control to the output beam patterns and 2) matches transducers of different size or type within the loudspeaker array.

16. An article of manufacture, comprising:
a non-transitory machine-readable storage medium that stores instructions which, when executed by a processor in a computing device,
sample one or more audio streams to produce a matrix of one or more samples;
multiply the matrix of one or more samples with a beam pattern mixing matrix, which represents a plurality of predefined modal patterns, to produce a modal gain value for each of the plurality of predefined modal patterns; and
multiply a matrix of the modal gain values with a modal decomposition matrix to produce a driving signal for each of a plurality of transducers in a speaker array to produce one or more output beam patterns.

17. The article of manufacture of claim 16 , wherein the beam pattern mixing matrix is a matrix of real numbers representing weights for the predefined modal patterns to produce a separate output beam pattern for each of the one or more audio streams,
wherein the matrix of the modal gain values includes individual real number coefficients for each of the predefined modal patterns,
wherein the modal decomposition matrix is a matrix of real numbers representing assignment levels for each predefined modal pattern to each transducer in the loudspeaker array such that the transducers in the loudspeaker array produce each of the predefined modal patterns based on weights in the beam pattern mixing matrix.

18. The article of manufacture of claim 16 , wherein the non-transitory machine-readable storage medium includes further instructions that when executed by the processor:
filter each modal gain value in the matrix of modal gain values using a separate modal filter, wherein each modal filter corresponds to a separate modal pattern in the plurality of predefined modal patterns and each modal filter boosts a power level

Assignees

• Apple Inc

Inventors

• Johnson Martin E
• Dix Gordon R
• Prabakaran Vijay G
• Saux Tom-Davy William Jendrik

Classifications

• H04R1/403 Primary

  loud-speakers · CPC title

• H04R2201/40

  Details of arrangements for obtaining desired directional characteristic by combining a number of identical transducers covered by H04R1/40 but not provided for in any of its subgroups · CPC title

• H04R2201/401

  2D or 3D arrays of transducers · CPC title

• H04R5/02

  Spatial or constructional arrangements of loudspeakers · CPC title

• H04R3/12

  for distributing signals to two or more loudspeakers {(specially adapted for hearing aids H04R25/407)} · CPC title