A detector for acoustic directionality

This paper describes the principles, construction and performance of a new type of acoustic directional detecting instrument. It is intended for borehole operation and is adapted to a circularly confined space. The operating principle lies in the orientational pinning of resonator vibrational modes to the pressure gradient of the sound source. In its simplest form, a pair of antinodes lines up with the source direction. The resonator consists of a metal hemi-spherical shell suspended at its apex, and equipped with semi-conductor strain gauges. The encapsulated device has been tested in water and presently achieves an accuracy of 2°.