An Innovative Structure Design for an Electromagnetic MEMS Speaker with Optimized SPL and THD Performance

This study presents a low-power electromagnetic MEMS speaker featuring a novel structural design to improve both sound pressure level (SPL) and total harmonic distortion (THD). Two key design strategies are implemented: (1) Coil position and structure improvement — the driving coil is relocated from the diaphragm perimeter toward its center to enhance the fundamental vibration mode, resulting in an SPL increase of about 5 dB in the low-frequency range. (2) Central stiff mass block integration — a rigid mass is introduced at the diaphragm center to suppress higher-order modal coupling, achieving a 19% reduction in average THD below 10 kHz. Measurements performed in a pressure-field ear simulator demonstrate that the proposed design achieves 106 dB SPL at 1 kHz with only 0.03 mW power consumption, indicating a significant improvement in acoustic efficiency compared to previous studies. The design shows strong potential for in-ear acoustic applications, such as true wireless earbuds and hearing aids.