Design exploration of shell-structured distributed mode loudspeakers via coupled acoustic-vibrational analysis

Distributed Mode Loudspeakers (DMLs) utilize bending waves on flat plates to produce acoustic radiation and have gained attention due to their wide directivity and high loudness levels. However, their large physical size and limited design flexibility remain significant challenges. To address these limitations, shell-structured DMLs, which employ diaphragms with arbitrary curvature to induce coupling between in-plane and out-of-plane waves, have recently emerged as a promising alternative. This study investigates how two fundamental shape parameters—aspect ratio and curvature radius—influence the acoustic characteristics of shell-structured DMLs. A coupled simulation framework was employed, integrating an equivalent circuit model of the exciter, boundary element analysis of diaphragm vibrations, and finite element analysis of the resulting sound field in air. The simulation results indicate that a sufficient aspect ratio is critical to acoustics radiation, because acoustics radiation from longitudinal waves is promoted by effective wave coupling triggered Poisson effect. While the curvature-to-wavelength ratio significantly affects both resonant frequency and radiation efficiency. These findings offer foundational insights into shaping and optimizing shell-based DMLs, and contribute to a deeper understanding of their design space. The proposed methodology may facilitate the development of compact, tunable loudspeakers for next-generation audio systems.