Design of dual-frequency piezoelectric MEMS microphones for wind tunnel testing

The demand for aeroacoustic measurement microphones is surging in recent years as new rules on noise reduction and environmental compliance are getting tougher. However, the state-of-the-art microphones including classical measurement microphones and micro-electro-mechanical systems (MEMS) microphones cannot fully meet the strict requirements for wind tunnel testing (WTT) in terms of form factor, acoustic performance, and product price. To break through the bottleneck, a new type of piezoelectric MEMS microphones with dual frequency bands was designed as key part of a dedicate WTT solution, which aims to capture the unsteady pressure fluctuations underneath the turbulent boundary layer and predict the cabin noise excitation. The finite element method (FEM) was applied to analyze and optimize the MEMS design at the system level. The feasibility of the new MEMS design has been preliminarily verified by characterizing the mechanical and electrical properties of first batch of dual-frequency piezoelectric MEMS microphones. The acoustic characterization was conducted to evaluate the overall performance and the system-level FEM model was refined based on the measurement results.