Design of the silicon membrane of high fidelity and high efficiency MEMS microspeaker

This study presents a novel approach to MEMS microspeakers design aiming to tackle two main drawbacks of conventional microspeakers: their poor sound quality and their weak efficiency. For this purpose, an acoustic emissive surface based on a very light but very stiff structured silicon membrane was designed. This architecture, for which the membrane undesirable vibration modes were reduced to only five within the microspeaker bandwidth, is promising to let the microspeaker produce high sound quality from 300 Hz to 20 kHz. This silicon membrane is suspended by a whole set of silicon springs designed to enable out-of-plane displacements as large as 300 μm. Different geometries of springs were considered and the material maximum stress was analyzed in each case by finite element modeling. The proposed structure promises an efficiency of 10^-4, that is to say ten times higher than that of conventional microspeakers.