Highly miniaturized 115 dB full-range MEMS loudspeaker for in-ear applications

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 mm2, the highly miniaturized loudspeaker achieves high sound pressure levels (SPL) of 115 dB SPL and 95.7 dB SPL/mm2 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.