1. INTRODUCTION
In the 1970s, work by Gerzon and others on Ambisonics established the use of spherical microphone and loudspeaker arrays for capturing and recreating three-dimensional sound fields [1], [2]. However, it hasn't been until recently that a more rigorous understanding of higher order spherical arrays has been established [1], [2], [3], [4]. It is now well known that the capture ability of spherical microphone arrays is limited in the high frequencies by spatial aliasing and in the low frequencies by microphone placement, mismatch, and SNR concerns. Incorporating a white noise gain (WNG) constraint into the beamformer design can ensure that a beam pattern remains controlled at low frequencies [5].