A Mechanically-Open and Acoustically-Closed Piezo-Mems Speaker for in-Ear Applications

This work presents an innovative piezoelectric Micro-Electro-Mechanical System (MEMS) speaker for in-ear applications based on the new mechanically-open and acoustically-closed design concept. It shows very promising performances, i.e. a Sound Pressure Level (SPL) greater than 102 dB in the whole audible range for actuation voltages in the range 0-30 V and a compact footprint of 4.5x4.5 mm
²
. It represents the first step towards a new class of high performances piezo-MEMS speakers that do not require further additional closing membranes to minimize acoustic losses. A first prototype was numerically simulated during the design phase, fabricated by STMicroelectronics and experimentally characterized. A very good numerical-experimental matching was finally demonstrated.