Design and modeling of a novel piezoresistive microphone for aero acoustic measurements in laminar boundary layers using FEM and LEM

In this paper the modeling and simulation results of a piezo-resistive microphone are presented and a possible fabrication process flow and characterization concept of the sensor are described. The main objective in this funded AEROMIC project is to develop a thin and small in size microphone, which can be integrated into a flexible array, that can be mounted onto an airplane hull for flight tests. The microphone array should be no thicker than 2 mm and should contain more than 80 flush mounted single microphones, allowing acoustic measurement without disturbance of the laminar boundary layer. The pitch of the microphone sensors in the array enable high spatial resolution of the pressure fluctuation. The optimization of geometry of single sensor microphone has been done using FEA (Finite Element Analysis). For the optimization of the geometry of the single microphone chip, FEA of the air damped dynamic behavior of the diaphragm is modeled in Ansys Harmonic Response Analyses with Acoustics ACT package. To model the array on system level, a lumped-element model (LEM) is set up to predict spatial resolution and signal to noise ratio. Derived from the FEA results, a sensor chip layout with three membrane sizes is presented.