Performance benefits of spherical diffracting arrays versus free field arrays

There are applications where microphone arrays must be integrated into/onto a structure. As an example there are efforts to instrument soldiers´ helmets and vehicles with sensors in order to detect and localize noise events. In these cases the sound will be diffracted around the support platform. In this paper a spherical diffracting platform is used and is shown to improve low frequency performance. The sphere was chosen as its diffraction can be modeled analytically and it is similar to a helmet. Specifically, this paper will compare both theoretical and experimental results for spherical free field and diffracting arrays of identical geometries to examine the effect diffraction has on the array performance. Singular values of the array manifold matrix will be compared to show that diffracting arrays outperform free field arrays, especially at lower frequencies.