Novel Type of MEMS Loudspeaker Featuring Membrane-Less Two-Way Sound Generation

In this paper a novel type of piezoelectric microelectromechanical loudspeaker is presented. The device concept is based on concentrically cascaded lead zirconate titanate actuators making it the first integrated two-way MEMS speaker reported. As a further novelty, the device is designed to operate without a closed membrane significantly improving the acoustic performance, energy efficiency, and manufacturability. Extensive finite element analysis studies have revealed a very high SPL of more than 79 dB in 10 cm distance at 500 Hz for a device 1 cm² in size operated at 30 V. At higher frequencies even larger SPL values are calculated enabling a flat frequency response with 89 dB for frequencies above 800 Hz. Based on this concept first speaker prototypes have been fabricated using MEMS technology.