Modelling of wide frequency range silicon microphone for acoustic measurement

This work demonstrates with numerical simulations, the feasibility of a wide frequency range and high pressure level piezoresistive microphone based on MEMS technology. An accurate lumped-element model was used to optimize the microphone dynamic response. Mechanical lumped parameters were extracted from structural finite element method (FEM) simulations, while squeeze film fluid parameters were extracted from FEM simulation of linearized Reynolds’s equation. Finally, acoustic radiation parameters were extracted from a weak coupling between the FEM and the boundary element method (BEM). Microphones with rectangular and circular membrane, vibrating in bending mode and suspended by four beams were simulated. In both cases we were able to achieve the specifications required for aero-acoustic applications: A flat frequency response up to 980 kHz and a sensitivity of about 10.5 μV/Pa. The electrical noise and mechanical thermal signal to noise ratio were 6.4 μV/Pa and 67 dB respectively.