A piezoelectric MEMS loudspeaker for in-ear and free field applications lumped and finite element models

This paper presents the simulation results of a piezoelectric MEMS loudspeaker. The micro-fabricated device is composed of two wafers, the first one features two bending piezoelectric actuators with large displacements, and the second one features a mobile rigid plate surrounded by a small interstice providing a thermoviscous layer hence avoiding an acoustic short circuit between its front and back sides. Performances of the loudspeaker are evaluated using a lumped element model and a finite element model to estimate the pressure generated by the loudspeaker in free field and in an ear-occluded coupler. Size variants of the design and their models are presented. The current design allows a radiated pressure of 80 dB SPL from 500 Hz at 10 cm and at 30 V pp for a 64 mm 2 footprint in free field, and more than 130 dB SPL in a IEC 60318–4 coupler with the same actuation voltage, which is above the known performances of the state of the art for MEMS loudspeakers with such dimensions. • Modeling the sound pressure level radiated by a MEMS loudspeaker using lumped element model • Ear-occluded coupler simulation using finite and lumped elements models • Maximum stress analysis of MEMS loudspeaker • Optimizing the radiated sound pressure level at 1 kHz for a small footprint • Increasing the efficiency of the loudspeaker by a two wafers manufacturing process