Impact of structural support on vector sensor acoustic performance

Abstract

Vector sensors hold great promise for the exploitation of undersea acoustics by providing the ability to measure the acoustic intensity. Current sensor developments can measure the acoustic acceleration in three dimensions as well as the pressure, which when combined through a cross‐correlation produces the acoustic intensity field surrounding the sensor. Mathematical studies indicate that a gain of 4.6 dB is achievable by beamforming the sensor’s three cardioid outputs with the pressure sensor’s omnidirectional response. In these studies, the mechanics of physically retaining the sensor in position is not considered, but is necessary to allow the sensor to freely sense particle velocity/acceleration and not shadow the sensor to the surrounding pressure field. A set of PVC frames was constructed to hold an individual sensor, which was then combined to form an array of sensors for use in a long‐term shallow water acoustic field intensity study. These frames are modeled to determine the level of forward and backscatter caused by the flooded PVC pipes and the possible impact to the theoretical patterns. The physical structures are then calibrated in a controlled measurement facility to determine if the accelerometers move freely in all three dimensions to generate the cardioid patterns necessary to achieve the gains predicted by intensity models over similar pressure sensor configurations.