Abstract
This study demonstrates a piezoelectric MEMS microspeaker containing triple reverse-trapezoid cantilever membranes. A unique driving method is also presented. The design features: (1) reverse-trapezoid cantilever membranes providing better electro-acoustic efficiency, (2) two additional reverse-trapezoid units in higher frequencies expanding the overall bandwidth, (3) a unique driving method, which named the enhanced terminated driving method can solve the SPL response issue by suppressing the unwanted motion, (4) the center anchor design can enhance the fault tolerance of the fabrication and decrease the disturbance among membranes. The proposed microspeaker shows SPL (Sound-Pressure-Level) above 80 dB within the frequency range of 1.0 kHz 8.0 kHz when actuated by 0.707 Vrms+7 V DC and above 70 dB from 1.0 kHz 14.1 kHz. The proposed design could be integrated with common dynamic drivers to compensate the insufficient SPL at higher frequencies.