June 10, 2011
A series of micro-electromechanical system (MEMS) based devices for acoustic direction finding have been designed and fabricated which mimic the aural system of the Ormia ochracea fly and its extraordinary directional sensitivity. To overcome the minimal spatial separation between its ears, a flexible hinge mechanically couples the fly's two tympanic membranes. Because of this coupling, the phase differences due to the time difference of arrival (TDOA) are greatly amplified and sound source direction is determined with unparalleled speed and accuracy. This unique system allows the fly to acoustically locate crickets which chirp with wavelengths two orders of magnitude greater than the dimensions of the hearing system. Extending earlier research into the mechanical characterization of the actual fly's hearing system, the presented research combines finite element modeling and experimentation to characterize the physical phenomena that affect the performance of the various MEMS designs. Specific investigations reported include damping effects, device linearity to sound pressure, and the effects of various packaging schemes on device performance. Results include successful demonstrations of several directional sensors responsive to both sinusoidal and impulsive sources, an electronic readout scheme using capacitive comb fingers, an asymmetric design for dual frequency use, and devices effective into the ultrasonic range, all of which could ultimately contribute to a millimeter-scale device for sniper-location or a number of other defense applications.
Lieutenant Commander Michael Touse is an Engineering Duty Officer in the U.S. Navy and a PhD Candidate in the Physics Department at the Naval Postgraduate School. After graduating from the U.S. Naval Academy in 1997, he served aboard the USS JOHN YOUNG (DD 973) as Anti-Submarine Warfare Officer and Navigator, then aboard the USS CHOSIN (CG 65) as Main Propulsion Assistant. He completed his Master's Degree at the Naval Postgraduate School in 2003 where he conducted characterization experiments on a two-color Quantum Well Infrared Photodetector. LCDR Touse then served as a Project Officer at the Mid-Atlantic Regional Maintenance Center in Norfolk, VA, until 2006 when he reported as the C4I Systems Maintenance Officer aboard the USS MOUNT WHITNEY (LCC 20) in Gaeta, Italy. After completing his doctoral research in June, 2011, he will transfer to the Program Executive Office for Integrated Warfare Systems in Washington, D.C.