Multi-resonant sub-wavelength acoustic vector sensor for underwater environments

This paper reports on a multi-resonant micro-electromechanical systems (MEMS) based acoustic vector sensor (AVS) capable of determining the direction of arrival (DOA) of various underwater sound sources. The AVS consists of two MEMS sensors aligned orthogonally and an omni-directional hydrophone. Signals from the sensors are directed to a microprocessor which conditions the data and calculates DOA. The AVS provides unambiguous 360° coverage, calculated in real time. This paper follows up on research into single-resonant sensor designs. This multi-resonant design represents important changes in sensor design characteristics and offers significant improvements in signal-to-noise ratio (SNR), bandwidth, and provides lower frequency detection capability than the single-resonant design. Data for this research were collected at a Navy facility designed for underwater acoustic experimentation. It minimizes underwater acoustic reflections. In the experiment, a stationary underwater acoustic source projected multiple acoustic signals while the AVS was rotated to adjust the DOA of the sound. The DOA accuracy of the AVS was measured over a 360° rotation for various sound sources. The average DOA error over a full rotation was measured to be less than 4.5°. These results indicate that this MEMS-based AVS is very attractive for many naval and other underwater acoustics applications.