A validated modeling strategy for piezoelectric MEMS loudspeakers including viscous effects

Piezoelectric micro-electro-mechanical system (MEMS) loudspeakers are drawing more interest due to their applications in new-developing audio technologies. MEMS devices' small dimensions necessitate including thermal and viscous effects in the surrounding air when simulating their behaviors. Thus, the linearized mass, momentum and energy conservation equations are used to describe these effects. These formulations are implemented in our open-source finite element program openCFS. In this article, we model a 3D piezoelectric MEMS loudspeaker in two configurations: open and closed back-volume, which behave differently due to the effects of air viscosity and pressure forces between the cantilever and the closed back-volume. Furthermore, using a customized vacuum chamber, the atmospheric pressure is varied and its effects are studied in these two configurations, numerically and experimentally. Experimental results prove that our model predicts the behavior of the piezoelectric MEMS loudspeaker in various configurations very well. Additional simulations illustrate the effect of the slit thickness and thermal losses.