The polar pattern for a microphone or loudspeaker is its gain along a circle of constant radius away from the diaphragm/driver. For a sphericalwave ``pointsource'', the polar pattern is simply a constant at each radius, e.g., , where denotes the pressurescaling at and denotes the distance from the center of the source.
Since our speaker arrays are typically flat, we need to calculate a slice through the polar pattern along a listening line (or plane) which we will take to be parallel to the array and to the axis, as shown in Fig.15. The polarpattern slice is then be considered as one sample (interpolation kernel) used to reconstruct the soundfield at a distance from the array.

http://arxiv.org/abs/1911.07575
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