Piezoelectric Mems Microspeaker with Suspension Springs and Dual Electrode to Enhance Sound Pressure Level

Abstract

This study based on piezoelectric actuating principle to design and realize a high sound pressure level (SPL) MEMS microspeaker for in-ear applications. The proposed suspension-spring design enables larger out-of-plane displacement to improve SPL and the piston movement of diaphragm to generate sound waves with better quality. Moreover, applying dual electrode pattern on the suspension springs further enhances diaphragm out-of-plane displacement and SPL. Measurements demonstrate the highest SPL above 100dB at 3.13kHz in a 3cm long canal. SPL higher than 70dB is obtained from 400Hz to 8.5kHz with only 2V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> driving voltage and 1.67mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> diaphragm. Furthermore, total harmonic distortion (THD) is less than 3% in most of the audio range.