RESOLVING BEARING AMBIGUITY WITH A SINGLE BIO-INSPIRED DIRECTION-FINDING MEMS ACOUSTIC SENSOR

Abstract

Microelectromechanical systems (MEMS) based directional sound sensors have been developed to mimic the unique hearing mechanism of the parasitoid fly Ormia ochracea. The fly appears to analyze the superposition of the two natural oscillation modes (rocking and bending) of the coupled eardrums to identify the incident direction of the cricket chirp. This approach allows it to accurately determine the direction of sound using wavelengths that are much longer than the gap between the fly's hearing organs. The sensor developed by NPS consists of two wings that are attached to a substrate using two torsional legs at the middle, as detailed in several previous theses. The current detection systems based on the fly’s hearing system requires two sensors to uniquely determine the direction since only one mode is utilized. This study focuses on the use of a single MEMS sensor by analyzing the superposition of the rocking and bending modes in order to produce a sensor that directly mimics the parasitoid fly while reducing the overall size of the device. The measurements show that signals from the two wings can be processed to uniquely determine the direction of sound. In addition, the measurements agreed with that of simulations utilizing finite element modeling. The findings indicate that MEMS based sensors having dimensions much smaller than the wavelength of sound they detect can be developed to accurately determine the bearing of incident sound.