Novel membrane-less two-way MEMS loudspeaker based on piezoelectric dual-concentric actuators

In this paper a novel type of piezoelectric MEMS loudspeaker is presented. The device concept is based on concentrically cascaded PZT actuators making it the first two-way MEMS speaker reported. As a further novelty, the device is designed to operate without a closed membrane offering significant improvements with respect to acoustic performance, energy efficiency and manufacturability. Extensive FEA studies have revealed a very high SPL of more than 85 dB at 500 Hz for a device 10 × 10 mm2 in size. At higher frequencies even larger SPL values are achieved enabling a flat frequency response with 95 dB for frequencies above 800 Hz. Based on the concept speaker prototypes have been fabricated using MEMS technology and are currently being characterized.