A microelectromechanical system (MEMS)–based directional sound sensor has been developed to
operate both in air and underwater. The sensor consists of two wings that are attached to a substrate using
two torsional legs at the middle as detailed in several previous theses. Though it was highly successful in
operating in the air application, its underwater operation required it to be immersed in a liquid with
impedance matching housing. The fluid strongly alters the operating characteristics of the sensor and
reduces the sensitivity due to added viscous damping. In this thesis, two new MEMS sensors, designed to
operate at 300 Hz and 520 Hz, were characterized both in air and underwater. For the measurements, the
MEMS sensors were first integrated with newly designed readout electronics, which were needed to
overcome the problems encountered with the off-the-shelf electronics employed in earlier studies. The new
electronics were found to be highly stable and operated well when immersed in silicone oil used for
underwater packaging of the sensors. The measured frequency responses were found to match with that of
the simulations carried out using COMSOL finite element modeling. In addition, the sensors also show
expected cosine directional characteristics. The research findings show that the MEMS-based sensors can be
successfully operated in an underwater environment for determining the bearing of sound sources.Outstanding ThesisLieutenant, United States NavyApproved for public release; distribution is unlimited
