1/19 Philip Coleman, Philip J. B. Jackson, Marek Olik 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) 15 th July 2014 Paper #558, Session SS28D

2/19 Stereophonic personal audio reproduction using planarity control optimization Personal sound is an active research topic

3/19 Stereophonic personal audio reproduction using planarity control optimization Two main approaches to sound zones [1] -Energy cancellation -Least-squares error minimization Previous reported results limited to mono Likely requirement for stereo from consumers We 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 , 2014.

4/19 Stereophonic personal audio reproduction using planarity control optimization Create two virtual loudspeakers and quiet zone Require control of energy direction Target listener gets stereo image Listener in quiet zone undisturbed

5/19 Stereophonic personal audio reproduction using planarity control optimization Zone A Zone B

6/19 Stereophonic personal audio reproduction using planarity control optimization Planarity control (PC) [2] constraint on source weights dark zone energy bright 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 [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.

7/19 Stereophonic personal audio reproduction using planarity control optimization Planarity control (PC) -Steering matrix [4] -Pass-range microphones angles [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.

8/19 Stereophonic personal audio reproduction using planarity control optimization 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.

9/19 Stereophonic personal audio reproduction using planarity control optimization 60 channel circular circular array Two 25 × 35 cm zones Calculate weights for each frequency (A/B;L/R) Independent performance measurement set

10/19 Stereophonic personal audio reproduction using planarity control optimization Acoustic contrast RMSE of energy direction

11/19 Stereophonic personal audio reproduction using planarity control optimization Measured acoustic contrast (both channels)

12/19 Stereophonic personal audio reproduction using planarity control optimization Accuracy of energy placement Left channelRight channel

13/19 Stereophonic personal audio reproduction using planarity control optimization Some higher frequencies have higher RMSE -Some energy at target location Measured PC left channel 2350 Hz

14/19 Stereophonic personal audio reproduction using planarity control optimization Some higher frequencies have higher RMSE -Some energy at target location -Failure for some grating patterns PC Right PM Left PC Left 120 SPL (dB) 0 Free-field simulations, 2350 Hz

15/19 Stereophonic personal audio reproduction using planarity control optimization Hear for yourself!

16/19 Stereophonic personal audio reproduction using planarity control optimization Results summary -PC gives best contrast -PM gives best accuracy of energy direction -Differing behavior above array aliasing limit Hz Hz PCPMPCPM RMSE left (deg) RMSE right (deg) Combined contrast (dB)

17/19 Stereophonic personal audio reproduction using planarity control optimization Previous personal audio work in mono Extension to stereo investigated Implemented PC and PM on 60 channel circle PC gave up to 30dB contrast PC 6 dB greater contrast than PM (freq. ave., Hz) PM placement 1.2 degrees more accurate (channel & freq. ave., Hz) Further work should investigate perception

18/19 Paper #219, Session SS06A Interested in personal audio? Stereophonic personal audio reproduction using planarity control optimization

19/19 Stereophonic personal audio reproduction using planarity control optimization Thanks to Alice Duque who made RIR measurements

20/19 Stereophonic personal audio reproduction using planarity control optimization Measure room responses (60 × 768) Calculate optimal source weights for each frequency for: -Zone A target, L/R virtual loudspeakers -Zone B target, L/R virtual loudspeakers Inverse FFT/shift to make FIR filters (× 60) Convolve with program material Independent performance measurement set