Abstract
Sound zone reproduction facilitates listeners wishing to consume personal audio content within the same acoustic enclosure by filtering loudspeaker signals to create constructive and destructive interference in different spatial regions. Published solutions to the sound zone problem are derived from areas such as sound field synthesis and beamforming. The first contribution of this thesis is a comparative study of multi-point approaches. A new metric of planarity is adopted to analyse the spatial distribution of energy in the target zone, and the well-established metrics of acoustic contrast and control effort are also used. Simulations and experimental results demonstrate the advantages and disadvantages of the approaches. Energy cancellation produces good acoustic contrast but allows very little control over the target sound field; synthesis-derived approaches precisely control the target sound field but produce less contrast. Motivated by the limitations of the existing optimization methods, the central contribution of this thesis is a proposed optimization cost function ‘planarity control’, which maximizes the acoustic contrast between the zones while controlling sound field planarity by projecting the target zone energy into a spatial domain. Planarity control is shown to achieve good contrast and high target zone planarity over a large frequency range. The method also has potential for reproducing stereophonic material in the context of sound zones. The remaining contributions consider two further practical concerns. First, judicious choice of the regularization parameter is shown to have a significant effect on the contrast, effort and robustness. Second, attention is given to the problem of optimally positioning the loudspeakers via a numerical framework and objective function. The simulation and experimental results presented in this thesis represent a significant addition to the literature and will influence the future choices of control methods, regularization and loudspeaker placement for personal audio. Future systems may incorporate 3D rendering and listener tracking.