Development of a compact suspension system for a neutrally buoyant underwater acoustic intensity probe

Abstract

Practical use of neutrally buoyant underwater acoustic intensity probes requires a suspension system to position them in some preferred orientation with respect to an acoustic field of interest. However, since these probes typically contain a moving coil geophone to facilitate particle velocity measurements, the design of such suspension systems is not trivial. On one hand, theory mandates that the dynamics of the geophone will not be adversely affected by the suspension as long as the mass-spring system created by the probe and the elastic members has a low-resonance frequency and high quality factor relative to that of the geophone. However, by meeting these two design criteria, wave effects (e.g., flexural resonances) in the elastic members can become a limiting factor in the performance of the device, particularly at high frequencies. This paper presents theoretical and experimental results of an effort to design a compact suspension system that embodies the aforementioned design considerations, but has relatively low susceptibilty to flexural resonances. [Work supported by the Acoustics Technology Branch of the Naval Air Warfare Center—Aircraft Division, via the DoD Small Business Innovation Research Program.]