New integrated full-range MEMS speaker for in-ear applications

This paper reports the concept, fabrication and characterization of a new kind of MEMS loudspeaker for in-ear applications. The piezoelectrically driven device is designed to operate without a closed membrane, which significantly improves the acoustic performance, efficiency, manufacturability and miniaturization capability. Measurements performed on prototypes mounted to an artificial ear simulator have revealed high sound pressure levels (SPL) of about 110 dB. In contrast to standard state-of-the-art in-ear speakers the SPL can be maintained up to 20 kHz leading to an extraordinarily flat frequency response using electronic equalization. Furthermore, low total harmonic distortion (THD) of less than 2 % and good energy efficiency of more than 105 dB/mW have been observed over almost the entire audio range.