Abstract
This study demonstrates the concept to monolithically integrate piezoelectric actuated structures of different natural frequencies on an SOI wafer to achieve the full-range MEMS speaker array. First of the two major points featured in this research is leveraging the characteristic of micromachining technology to design, fabricate, and integrate multiple PZT actuation units on a single chip to enhance the performance of microspeaker. The second is the design of novel driving electrodes on two bridge structures and one clamped diaphragm (5 mm by 1.5 mm) activating different resonant modes to increase SPL (Sound Pressure Level) at low, medium and high frequencies. As a result, the full-range MEMS speaker array can be realized. Measurements in the standard ear simulator illustrate that with 3.5 Vrms driving voltage, the proposed microspeaker has SPL higher than 81dB in the full audio range, and even larger than 90 dB from 60 Hz to 15 kHz.