Speaker
Description
Research on modulated ultrasound microspeakers has been increasing steadily in recent years, with new modulation and actuation techniques being proposed. Such devices are highly integrated, often consisting of multiple moving parts and varying channel widths that require complex simulation to accurately model their behavior. This makes accurate simulations very challenging. In this contribution, we present a fully coupled multiphysics finite element model of a microspeaker comprising two moving membranes, a pressure chamber between them, and air channels with varying acoustic impedance. Incorporating electrostatic actuation, nonlinear membrane mechanics and a viscous air domain, the model aims to accurately capture surface traction and squeeze-film damping effects. Using a frequency-modulated excitation, the modulation behavior is investigated. In the spectrum of the resulting modulated ultrasound pressure signal, the low-frequency audio signal components are present, confirming the expected modulation behavior. Initial results indicate an increase in total harmonic distortion when nonlinear and viscous effects are included compared to a linear model. This provides crucial insight into the device's development and demonstrates the importance of a fully coupled simulation for predicting the modulation behavior. All steps, from modeling and meshing to the coupled simulation, were done using only open-source software (Gmsh, openCFS), providing a reproducible framework for simulation of highly coupled systems.