Paper #219, Session SS06A NUMERICAL OPTIMIZATION OF LOUDSPEAKER CONFIGURATION FOR SOUND ZONE REPRODUCTION • 15thJuly 2014 Philip Coleman,Philip J. B. Jackson, MarekOlik firstname.lastname@example.org Centre for Vision, Speech and Signal Processing, University of Surrey, Guildford, Surrey, GU2 7XH, UK Jan Abildgaard Pedersen Bang & Olufsen A/S (now with Dynaudio A/S, Sverigesvej 15, 8660 Skanderborg, DK)
Introduction • Personal sound is an active research topic
Introduction • Personal sound is an active research topic • A number of control strategies proposed   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]  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  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]  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.  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  ? ?  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  T. Takeuchi and P. A. Nelson, “Optimal source distribution for binaural synthesis over loudspeakers”, J. Acoust. Soc. Am. 112(6), p. 2786–2797, 2002  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 via www.posz.org
Approach • Sound zone source weights calculated with acoustic contrast control [9,10] constraint on source weights bright zone energy dark zone energy  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.  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  P. J. B. Jackson, F. Jacobsen, P. Coleman and J. Pedersen, “Sound field planarity characterized by superdirectivebeamforming”, in Proc. 21st ICA, Montreal, 2-7 June 2013.
Evaluation metrics • Generalizable set of metrics observed sound pressures in zone A number of observation microphones in zone B number of observation microphones in zone A observed sound pressures in zone B
Evaluation metrics • Generalizable set of metrics energy coincident with the principal plane wave direction total energy in the zone
Evaluation metrics • Generalizable set of 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   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 • +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)  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 zone Bright 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
Stereophonic personal audio reproduction using planarity control optimization Did you see my last talk? Paper #558 Numerical optimization of loudspeaker configuration for sound zone reproduction
Acknowledgements Thanks to Alice Duque who made RIR measurements email@example.com www.linkedin.com/in/philipcolemanaudio