Characterization of the MEMS Directional Sound Sensor in the High Frequency (15-20 kHz) Range

摘要

The Sensor Research Laboratory (SRL) at Naval Postgraduate School (NPS) has developed a micro-electromechanical system (MEMS) based directional sound sensors that mimics the aural system of the Ormia Ochracea Fly. The goal of this research is to characterize a set of directional sound sensors with varying configurations that operate in the high frequency range (15-20 kHz). The sensor consists of two identical wings coupled in the middle and the entire structure is connected to a substrate using two legs in the middle. In response to sound, the coupled wings oscillate with rocking and bending like motions at frequencies that depend on the mechanical characteristics of the structure. A simulation of sensor characteristics using COMSOL finite element software showed a resonant frequency of about 20 kHz for each device. The devices were fabricated by the MEMSCAP foundry service using silicon-on-insulator (SOI) substrate with a 25 m device layer. Using a laser vibrometer, response to incident sound pressure was measured at different frequencies and angles. All the devices showed that measured and simulated frequencies were in reasonably close agreement. The measurements showed good sensitivity to the direction of sound as predicted.