Microelectromechanical systems directional acoustic sensor for underwater applications

In this work, a MEMS-based directional acoustic sensor operating underwater is explored. The sensor operates in a narrow frequency band centered at the mechanical resonance. The studied sensor consists of two wings coupled by a bridge which is pivoted to a substrate. Interdigitated comb finger capacitors attached to the wings allow for electronic readout of the mechanical oscillations, which are proportional to the sound direction of incidence. For underwater testing, the sensor was immersed in silicone oil, contained by a urethane housing with near unity acoustic transmission. The characteristics of the MEMS sensor both in air and silicone oil were analyzed using finite element modeling. Performance of the sensor was characterized both in air and underwater. Measured underwater frequency response showed that the resonance frequency of the sensor was shifted to a lower value compared to that of in air. This is primarily due to mass loading from the silicone oil used for immersing the sensor. Peak sensitivity of the sensor was found to be about 6 mV/Pa or –165 dB re 1 V/mPa. The sensor showed good directional response with a dipole pattern. Results show the potential of MEMS sensors for underwater applications to detect the bearing of sound sources.In this work, a MEMS-based directional acoustic sensor operating underwater is explored. The sensor operates in a narrow frequency band centered at the mechanical resonance. The studied sensor consists of two wings coupled by a bridge which is pivoted to a substrate. Interdigitated comb finger capacitors attached to the wings allow for electronic readout of the mechanical oscillations, which are proportional to the sound direction of incidence. For underwater testing, the sensor was immersed in silicone oil, contained by a urethane housing with near unity acoustic transmission. The characteristics of the MEMS sensor both in air and silicone oil were analyzed using finite element modeling. Performance of the sensor was characterized both in air and underwater. Measured underwater frequency response showed that the resonance frequency of the sensor was shifted to a lower value compared to that of in air. This is primarily due to mass loading from the silicone oil used for immersing the sensor. Peak sensitiv...