Abstract
This study presents a novel approach and the electrode design to drive two particular vibration modes of the structure to improve the frequency range of the piezoelectric MEMS microspeaker. Extending the advantage of the spring-diaphragm structure to enhance low-frequency sound pressure level (SPL) in the previous work [1], the proposed design in this study not only sustains low-frequency SPL by the piston mode of the diaphragm actuating by the edge electrodes, but also further increases high-frequency SPL to improve frequency range by the drum mode excited by the central electrode on the diaphragm. Measurements in the standard ear simulator depict that the proposed design has a significant SPL enhancement after the first resonant peak and meanwhile maintains the performance at low frequencies. From 2.6 kHz ∼ 20 kHz, the proposed design shows an improvement of more than 15 dB SPL over the reference design.