Direction finding using a biaxial particle-velocity sensor

A particle-velocity sensor measures the acoustic particle velocity, instead of the acoustic pressure. A biaxial velocity-sensor (a.k.a. a “u–u probe”) consists of two uniaxial velocity-sensors, oriented orthogonally and (possibly) displaced in space. This paper investigates what orientations of the two axes would allow azimuth-elevation direction finding, what closed-form formulas to achieve this direction finding via eigen-based parameter-estimation algorithms, and what the corresponding Cramér–Rao bounds would be.