All the source models in beamshapes are tested for their correctness by comparing
with published results. As of version 0.2, the models and their outputs are tested by
comparing the beamshapes output with plots in Beranek & Mellow 2012.
Bernanek & Mellow 2012 calculate two types of directivity patterns: 1) the 'on-axis' pattern which describes the on-axis sound intensity across different ka values for instance, and 2) the 'full' directivity pattern, looking at the relative sound intensity (re. on-axis level) across the azimuth, and for different ka values.
Tests pass if they are within the threshold of the published pattern.