Bio-Inspired Rectangular Shaped Piezoelectric MEMS Directional Microphone

Abstract

The noise floor of a piezoelectric MEMS directional microphone largely depends on piezoelectric materials and transducer modes. A careful choice of these parameters (piezoelectric materials and transducer modes) can help to significantly improve the difficulties of noise floor. Here, we present a unique diaphragm-based biomimetic MEMS directional microphone having multiple-port sensing schemes. The diaphragm is separated into two wings and supported by two torsional beams, which are hinged to a fixed support as to imitate the unique inter-tympanal feature of the fly Ormia ochracea. In this microphone, the thermal-mechanical noise (Johnson noise) is minimized by adopting aluminium nitride-based piezoelectric sensing. The d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">33</sub> mode is incorporated with a prime focus on sensitivity enhancement which leads to signal-to-noise ratio improvement. Measured directivity patterns of both wings show a strong agreement with the direction of applied acoustic pressure as expected for an ideal bi-directional microphone. The measured noise floor at 1-kHz frequency and overall A-weighted noise floor across the audio frequency are 31.35 dB SPL and 32.5 dBA, respectively, which are quite less than some notable works on directional microphones. The experimental results verify the uniqueness of this work.