Www.posz.org 1/23 Philip Coleman, Philip J. B. Jackson, Marek Olik [email protected] Centre for Vision, Speech and Signal Processing, University

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NUMERICAL OPTIMIZATION OF LOUDSPEAKER CONFIGURATION FOR SOUND ZONE REPRODUCTION

Philip Coleman, Philip J. B. Jackson, Marek [email protected]

Centre for Vision, Speech and Signal Processing,

University of Surrey, Guildford, Surrey, GU2 7XH, UK

Jan Abildgaard PedersenBang & Olufsen A/S

(now with Dynaudio A/S, Sverigesvej 15, 8660 Skanderborg, DK)

15th July 2014

Paper #219, Session SS06A

www.posz.org2/23Numerical optimization of loudspeaker configuration

for sound zone reproduction

Introduction

• Personal sound is an active research topic



Introduction

• Personal sound is an active research topic

• A number of control strategies proposed [1]

[1] P. Coleman, P. J. B. Jackson, M. Olik, M. Møller, M. Olsen, and J. Pedersen, “Acoustic contrast, planarity and robustness of sound zone methods using a circular loudspeaker array,” J. Acoust. Soc. Am. 135(4), p.1929-1940, 2014.



Introduction

• Loudspeaker arrays for personal audio:- Compact line array [e.g. 2,3]

[2] J.-H. Chang, C.-H. Lee, J.-Y. Park, and Y.-H. Kim, “A realization of sound focused personal audio system using acoustic contrast control,” J. Acoust. Soc. Am. 125(4), p. 2091–2097, 2009[3] Simón-Gálvez, M. F., Elliott, S. J., & Cheer, J. “The effect of reverberation on personal audio devices.” J. Acoust. Soc. Am. 135(5), 2654-2663, 2014.



Introduction

• Loudspeaker arrays for personal audio:- Compact line array - Circular array [e.g. 4,5]

[4] F. Jacobsen, M. Olsen, M. Møller, and F. Agerkvist, “A comparison of two strategies for generating sound zones in a room,” in Proc. 18th ICSV, Rio de Janeiro, Brazil, 10-14 July 2011. [5] M. Shin, S. Q. Lee, F. M. Fazi, P. A. Nelson, D. Kim, S. Wang, K. H. Park, and J. Seo (2010), “Maximization of acoustic energy difference between two spaces,”. Acoust. Soc. Am. 128(1), p. 121-131, 2010



Introduction

• Loudspeaker arrays for personal audio:- Compact line array- Circular array

• Both array types may have benefits• Users may have some freedom to position

loudspeakers• We investigate optimal loudspeaker placement



Introduction

• Best positions for N loudspeakers ?• Can optimized arrays give…

- Improved cancellation?- Better control of target sound field?- Reduced power consumption?- Increased robustness?- Improved compensation for room?

??

?



Introduction

• Previous work- Crosstalk cancellation [6,7]

- Sound zones [8]

??

?

[6] M. R. Bai, C.-W. Tung, and C.-C. Lee, “Optimal design of loudspeaker arrays for robust cross-talk cancellation using the taguchi method and the genetic algorithm,” J. Acoust. Soc. Am. 117(5), p. 2802–2813, 2005[7] T. Takeuchi and P. A. Nelson, “Optimal source distribution for binaural synthesis over loudspeakers”, J. Acoust. Soc. Am. 112(6), p. 2786–2797, 2002

[8] P. Coleman, M. Møller, M. Olsen, M. Olik, P. J. B. Jackson, and J. Pedersen (Abstract), “Performance of optimized sound field control techniques in simulated and real acoustic environments,” in J. Acoust. Soc. Am., 131(4), p. 3465, 2012. Presented at Acoustics 2012, Hong Kong, 13-18 May 2012, available viawww.posz.org



Approach

• Sound zone source weights calculated with acoustic contrast control [9,10]

constraint on source weights

dark zone energy bright zone energy

[9] J-W. Choi and Y-H Kim, “Generation of an acoustically bright zone with an illuminated region using multiple sources”, J. Acoust. Soc. Am. 111, 1695–1700, 2002.[10] Elliott, S. J., Cheer, J., Choi, J. W., & Kim, Y. Robustness and regularization of personal audio systems. IEEE Trans. ASLP, 20(7), 2123-2133, 2012.



Evaluation metrics

• Generalizable set of metrics

Evaluation metric Linked characteristics

Contrast Minimal interference

Planarity [11] Spatial sound distribution

Control effort Robustness, low electrical power

[11] P. J. B. Jackson, F. Jacobsen, P. Coleman and J. Pedersen, “Sound field planarity characterized by superdirective beamforming”, in Proc. 21st ICA, Montreal, 2-7 June 2013.



Evaluation metrics



Planarity Spatial sound distribution


observed sound pressures in zone A

observed sound pressures in zone B

number of observation microphones in zone B

number of observation microphones in zone A




Evaluation metrics

energy coincident with the principal plane wave direction

total energy in the zone








Evaluation metrics

sum of squared loudspeaker weights

reference loudspeaker weight








Objective function

• Defined optimization cost function based on physical metrics

- Where

• Choose or optimize weighting coefficients• Could use perceptual model [12]

[12] J. Francombe, P. Coleman, M. Olik, K. Baykaner, P. J. B. Jackson, R. Mason, M. Dewhirst, S Bech and J. Pedersen, "Perceptually optimized loudspeaker selection for the creation of personal sound zones, in Proc. 52nd AES Int. Conf., Guildford, UK, 2-4 Sept. 2013.



Approach

• Sequential Forward-Backward Search [13]

- +2, -1

• Applied each element in turn• Focus here on contrast-only case

- Other results included in paper- Selected between 6 and 30 optimal positions - based on predicted performance

(mean at 100, 200, ..., 4000 Hz for both zones)

[13] P. A. Devijver and J. Kittler (1982), Pattern recognition: A statistical approach. Englewood Cliffs, NJ: Prentice/Hall International., p.220



Reproduction setup

• 60 channel circular candidate array

• Two 25 × 35 cm zones• Independent performance measurement set



Results

• Array configurations- 10 loudspeaker example

Contrast-only Arc Circle



Results

• Acoustic contrast (average over freq.)

- Circle worst over frequency- Optimal set best for 6 loudspeakers

Contrast-only



Results

• 10 loudspeakers over frequency

Contrast-only

6 dB

?



Results

• Sound pressure level- 2650 Hz notch, simulated in free-field

Contrast-only

Dark zoneBright zone



Summary

• Loudspeaker array geometries not previously investigated for sound zones

• Proposed objective function based on physical metrics

• Improved min. contrast by 6 dB compared to reference arrays (10 loudspeaker example)

• Further work should investigate:- Weighting of cost function- Extended loudspeaker sets- Advanced numerical search methods

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Stereophonic personal audio reproduction using planarity control optimization

Paper #558

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Numerical optimization of loudspeaker configuration for sound zone reproduction



Acknowledgements

www.linkedin.com/in/philipcolemanaudio

[email protected]

Thanks to Alice Duque who made RIR measurements

Documents

Www.posz.org 1/23 Philip Coleman, Philip J. B. Jackson, Marek Olik [email protected] Centre for Vision, Speech and Signal Processing, University