Multiphysical Finite Element Model of a Hearing Aid Piezoelectric Loudspeaker for Optimization Purposes

Piezoelectric materials are widely used in applications involving miniaturized components. The application of these materials in hearing aid loudspeakers, commonly called receivers, may present technical and economic advantages such as reduction in the number of components and manufacturing cost. The vibro-acoustic analysis of a piezoelectric loudspeaker involves the construction of multiphysical models. Analytical models of piezoelectric components can be found in literature, but these models are generally characterized by simple geometries and boundary conditions, thus, limiting their applicability to an optimization process. This work presents multiphysical numerical models of miniaturized loudspeaker prototypes. The numerical models were constructed using the finite element method (FEM). The loudspeakers themselves are composed of a piezoelectric diaphragm coupled to a small acoustic cavity. The multiphysical model includes piezoelectric, structural, and acoustic coupled FE models, and the acoustic model of the small cavity considers the thermal and viscous effects on acoustic propagation. The multiphysical models are validated experimentally using two prototypes fabricated in-house. After validation, two loudspeaker designs were proposed and optimized from the viewpoint of application to hearing aids by following a procedure based on genetic algorithm and Nelder-Mead methods.