Unsealed Piezoelectric MEMS Speaker with Rigid-Flexible Composite Membrane

Abstract In this paper, we propose an unsealed piezoelectric microelectromechanical systems (MEMS) speaker with rigid-flexible composite membrane, which can eliminate the membrane separation and the vibration displacement limitation at high driving voltage compared to that with the sealed rigid-flexible coupling membrane demonstrated in our previous work. Measurements performed on encapsulated prototypes mounted to an artificial ear simulator have revealed that in the human audible range of 20 Hz-20 kHz, higher than 68.5 dB SPL are obtained at 2 V, and greater than 89.6 dB SPLs are achieved at 10 V. Moreover, the SPL distribution and effective SPLs at each moment when playing the same song exhibit similar characteristics to those of a commercial electromagnetic one. This piezoelectric MEMS speaker achieves high SPLs meeting the basic hearing needs of the human, and will have excellent prospects for future wearable audio electronics.