Finite Element Analysis of underwater acoustic vector sensor

Acoustic sensor traditionally used for tracking and other applications by NAVY is the Omni directional hydrophone. In order to extract information on the location of noise sources, an array of hydrophones are used and the beam formed output of array provides this information. The vector sensor measures acoustic pressure as well as acoustic particle velocity at a single point in space. The main advantage of vector sensor over traditional hydrophone is that they outperform the hydrophone array with small aperture. This is accomplished by tri-axial accelerometer which measure acceleration and a hydrophone which measure acoustic pressure in all orthogonal directions. This paper presents the Piezoelectric and Acoustic structure analysis carried out in COMSOL software for a frequency range 100Hz to 6kHz. Directionality comparison between spherical and cylindrical hydrophone is carried out using piezoelectric interaction analysis whereas the Acoustic structure Eigen frequency analysis is carried out to determine the natural frequency of the unit in water. Analysis for four combinations of hydrophone and polyurethane casing were carried out, from which a cylindrical hydrophone and a spherical poly urethane casing emerged as a suitable combination for the vector sensor unit.