Highly Miniaturized in-ear MEMS Loudspeaker Featuring High SPL

In this paper, simulation, fabrication, and measurement results of MEMS loudspeakers for in-ear applications are presented. The speakers are based on a novel design concept, enabling exceptionally high sound pressure levels (SPL) at very small sizes. Fabricated speakers mounted in a prototype earphone and attached to an IEC 60318-4 ear simulator generate 105 dB SPL within the whole audible frequency range. With a device area of only 2.4 x 2.4 mm
²
, this yields a normalized SPL of 89.7 dB/mm
²
, exceeding the previous generation by 9.4 dB/mm
²
.