Philip Coleman Philip J B Jackson Marek Olik pdcolemansurreyacuk Centre for Vision Speech and Signal Processing University of Surrey Guildford Surrey GU2 7XH UK Jan Abildgaard ID: 411789
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STEREOPHONIC PERSONAL AUDIO REPRODUCTION USING PLANARITY CONTROL OPTIMIZATION
Philip Coleman, Philip J. B. Jackson, Marek Olikp.d.coleman@surrey.ac.ukCentre 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 #558, Session
SS28DSlide2
Introduction
Personal sound is an active research topicSlide3
Introduction
Two main approaches to sound zones [1]Energy cancellationLeast-squares error minimizationPrevious reported results limited to monoLikely requirement for stereo from consumersWe investigate stereophonic personal audio[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. Slide4
Background
Create two virtual loudspeakers and quiet zoneRequire control of energy direction
Target listener gets stereo image
Listener in quiet zone undisturbedSlide5
Background
Zone A
Zone BSlide6
Cost functions
Planarity control (PC) [2]constraint on source weightsdark zone energybright zone energy projected in to angular domain [
3]
[2] P
. Coleman, P. J. B. Jackson, M.
Olik
, and J. Pedersen, “Optimizing the planarity of sound zones,” in Proc. 52nd AES Int.
Conf
.
,
Guildford, UK, 2-4
Sept.
2013
.
[3]
Chang, J. H., Choi, J. W., & Kim, Y. H. (2010). A plane wave generation method by wave number domain point focusing. J.
Acoust
. Soc. Am., 128, 2758
.Slide7
Cost functions
Planarity control (PC)Steering matrix [4]Pass-rangemicrophonesangles
[4] 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.Slide8
Cost functions
Pressure matching (PM; plane-wave target) [5]pressure in the dark zone + bright zone reproduction error[5] M. Poletti, “An investigation of 2-d multizone surround sound systems”, in Proc.125th AES Conv., San Francisco, CA, 2-5 October 2008. Slide9
Reproduction setup
60 channel circular circular arrayTwo 25 × 35 cm zonesCalculate weights for each frequency (A/B;L/R)Independent performance measurement setSlide10
Evaluation
Acoustic contrastRMSE of energy directionSlide11
Results
Measured acoustic contrast (both channels)Slide12
Results
Accuracy of energy placementLeft channelRight channelSlide13
Results
Some higher frequencies have higher RMSESome energy at target locationMeasuredPC left channel 2350 HzSlide14
Results
Some higher frequencies have higher RMSESome energy at target locationFailure for some grating patternsPC RightPM LeftPC Left
120SPL (dB)0
Free-field simulations, 2350 HzSlide15
How does it sound?
Hear for yourself!www.posz.orgSlide16
Results
Results summaryPC gives best contrastPM gives best accuracy of energy directionDiffering behavior above array aliasing limit250-2000 Hz100-7000 Hz
PCPM
PC
PM
RMSE
left (deg)
4.2
2.8
40
4.1
RMSE right (deg)
4.5
3.6
6.3
5.2
Combined
contrast (dB)
26
20
15.7
12.1Slide17
Summary
Previous personal audio work in monoExtension to stereo investigatedImplemented PC and PM on 60 channel circlePC gave up to 30dB contrast PC 6 dB greater contrast than PM (freq. ave., 250-2000 Hz)PM placement 1.2 degrees more accurate (channel & freq. ave., 250-2000 Hz)Further work should investigate perceptionSlide18
Numerical optimization of loudspeaker configuration for sound zone reproduction
Paper #219, Session SS06AInterested in personal audio?
Stereophonic personal audio reproduction using planarity control optimizationSlide19
Acknowledgements
www.linkedin.com/in/philipcolemanaudiop.d.coleman@surrey.ac.ukThanks to Alice Duque who made RIR measurementsSlide20
Implementation
Measure room responses (60 × 768)Calculate optimal source weights for each frequency for:Zone A target, L/R virtual loudspeakersZone B target, L/R virtual loudspeakersInverse FFT/shift to make FIR filters (× 60)Convolve with program materialIndependent performance measurement set