Tuesday, May 23, 13:00 — 14:30
Jan Abildgaard Pedersen (Chair)
P25-01 Amplitude Panning between Beamforming-Controlled Direct and Reflected Sound
Franck Zagala (Presenting Author), Matthias Frank (Author), Julian Linke (Author), Franz Zotter (Author)
Loudspeaker beamformers such as commercial sound bars can be used to produce narrow beams of sound that mainly reach the listener on distinct reflection paths or the direct path in the room. What happens if such variable directivity loudspeakers create two simultaneous beams of sounds with the same signal, each of which pointing to another acoustic path in the room? What is the resulting perceived direction of such a phantom source, and how do changes of time and level differences in the signal pair affect the result? This paper investigates these questions by a listening experiment that employs an auralized 3rd order source.
Convention Paper 9805
P25-02 Sound Zones: On the Effect of Ambient Temperature Variations in Feed-Forward Systems
Martin Olsen (Presenting Author), Martin Bo Møller (Author)
The precondition for realizing personal sound zones, relying on multichannel feed-forward control, is the robustness in the characterization of the sound field inside the control regions. Achieving high separation depends on the ability to accurately estimate the acoustic transfer functions from a set of control loudspeakers to the zones. In this paper the assessment of ambient temperature variations is based on a front-to-rear scenario at low frequencies in a car cabin. Experimental studies in a production vehicle show significant performance decrease, when the temperature conditions in the playback situation differ from those present during the setup procedure. The main cause of the mismatch in the two sets of acoustic transfer functions is analyzed and potential compensation strategies are discussed accordingly.
Convention Paper 9806
P25-03 Assessing the Influence of Loudspeaker Driver Nonlinear Distortion on Personal Sound Zones
Xiaohui Ma (Presenting Author), Patrick J. Hegarty (Author), Lars G. Johansen (Author), Jakob Juul Larsen (Author), Jan Abildgaard Pedersen (Author)
The impacts of loudspeaker nonlinear distortion on sound zones are measured in an anechoic chamber. Two loudspeaker arrays, each with four equally spaced drivers, are used to generate two sound zones, one bright and one dark. Acoustic contrast control (ACC) and planarity control (PC) are employed as control methods. A 250 Hz sinusoidal signal is used as stimulus, and the target sound pressure level for the bright zone is 82 dB. Simulations based on measured transfer functions give acoustic contrast of 43.1 dB between the two zones whereas the experimentally measured acoustic contrast is only 32.1 dB for ACC, and 29.3 dB for PC. Nonlinear distortion contributes to this contrast loss according to spectrum measurements. Experiments also reveal that the nonlinear distortion can be controlled through regularization of the control effort; the regularization parameter has an optimal value which can balance the acoustic contrast and nonlinear distortion.
Convention Paper 9807