Practical experiences with inertial type underwater acoustic intensity probes

This paper outlines the general design requirements for inertial type underwater acoustic intensity probes. In contrast to the finite differencing approach employed by the two-hydrophone technique, inertial probes contain discrete sensors for measuring the acoustic pressure and particle velocity directly, without approximation. The pressure is typically measured with a piezoelectric hydrophone and the particle velocity is typically measured with either a moving coil geophone or a piezoelectric accelerometer. The sensors are ideally packaged in a compliantly suspended housing that is neutrally buoyant and contains no in-band modes. Design considerations for such probes are usually centered around the suspension system since practical experience dictates that this attribute presents the biggest hurdle in developing a novel device that has reasonable fidelity over a specified band. Other important attributes include sensor size, buoyancy effects, fluid viscosity, viscoelastic coatings, vibration isolation, signal cable dynamics, noise floor considerations, and susceptibility to flow-induced self-noise.