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.
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