Development and characterization of miniaturized, flush-mount, microelectromechanical systems (MEMS) piezoelectric pressure-fieldmicrophones for aeroacoustic applications

This paper describes the development and experimental characterization of miniaturized, flush-mount aeroacoustic pressure-field microphones designed for through-wall installation applications such as aeroacoustic microphone phased arrays and dynamic pressure sensing. The silicon microelectromechanical systems (MEMS) sensor utilizes an aluminum nitride piezoelectric sensing element and is fabricated using a novel, low-cost approach to creating backside electrical contacts to enable an ultra-smooth sensing surface. A miniaturized integrated electronic piezoelectric (IEPE) voltage preamplifier is located directly behind the sensor within a 3.18-mm diameter, 17-mm long package, representing a significant size reduction over precision condenser microphones. Characterization includes measurement of sensitivity, total harmonic distortion (THD), minimum detectable pressure (MDP), and full frequency response from below cut-on to beyond diaphragm resonance using both an acoustic and a reciprocal calibration method that is uniquely suited for piezoelectric transduction. Characterization of a group of 25 devices demonstrates similar performance to previously developed piezoelectric aeroacoustic microphones in a much smaller form factor, with an average sensitivity of 252 μV/Pa, ±3 dB bandwidth of 10 Hz to 54 kHz, minimum detectable pressure (MDP) of 37 dBSPL, and 3% THD limit in excess of 172 dBSPL.