Highly miniaturized 115 dB full-range MEMS loudspeaker for in-ear applications
Fabian Stoppel, Johannes Fankhänel, Thorsten Giese, Christian Eisermann, Isa Pieper, Fabian Lofink
Abstract
The demand for miniaturization, low power consumption and function integration in modern in-ear devices is ever-increasing. Loudspeakers based on microelectromechanical systems (MEMS) emerged as a promising solution, though their performance, particularly regarding sound pressure per device area, has not yet reached its full potential. In this work, a fully integrated true MEMS microspeaker utilizing rectangular actuators and SU-8 acoustic shields is presented. With an active area of only 3 × 3 mm 2 , the highly miniaturized loudspeaker achieves high sound pressure levels (SPL) of 115 dB SPL and 95.7 dB SPL/mm 2 across the entire audible frequency range, surpassing the current state of the art. Additionally, the device exhibits total harmonic distortions below 1 % and high sensitivities up to 134 dB SPL/mW over a broad frequency range. This novel approach lays the foundation for substantial future improvements of MEMS loudspeakers with further technological advances, like higher acoustic shields or the integration of piezoelectric multilayers. • Main challenge of MEMS speakers is to generate high sound pressure at small size. • Proposed speaker addresses this issue using acoustic shields and decoupled actuators. • MEMS speakers with design as small as 3 × 3 mm² have been fabricated. • 115 dB sound pressure level achieved within full audible range despite small size. • Measurements show low distortion and high energy efficiency.