On The Design of Piezoelectric MEMS Speaker Combining Central Cross-Diaphragm with Wing-Like Diaphragm to Improve Sound Pressure Level Bandwidth

This study demonstrates a piezoelectric MEMS microspeaker with novel structure design consisting of four wing-like diaphragms connected to a central cross-diaphragm, achieving both high SPL (Sound-Pressure-Level) and wide SPL bandwidth. The features of the design include: (1) wing-like diaphragm connected to the movable central cross-diaphragm to increase out-of-plane displacement hence pressure output. (2) creating two vibration modes in audio frequency range to contribute two SPL peaks without a zero in between, which effectively broaden the SPL bandwidth. Measurements show that the proposed microspeaker has 3 “-’ 6 dB SPL enhancement before 5 kHz, and also achieves a 70 dB bandwidth in the range of 3.3 kHz “-’ 17.8 kHz, outperforming the reference design, under 0.7 Vrms+ 9 VDC driving signal in standard ear simulator.