A fly-inspired multi directional MEMS microphone

Abstract

Inspired by the hearing mechanism of the fly Ormia Ochracea, we demonstrated a MEMS diaphragm capable of pressure and pressure gradient sensing in two orthogonal directions. The diaphragm is circular and suspended by multiple spring arms along its circumference. Each spring contains a piezoelectric film on its top surface. The structure has many orthogonal vibration modes. These modes are used for the concurrent measurement of sound pressure and pressure gradient along two orthogonal axes by way of summing and subtracting signals generated by the various sensing ports. Vibration modes of the MEMS are measured by applying broadband chirp voltage waveforms to a piezoelectric sensing port while observing the resulting motion using a scanning laser Doppler vibrometer (LDV). The device was then packaged for acoustic measurements by integrating each of several ports with a high input impedance Integrated Circuit Amplifier (ICA). Acoustical sensitivity and directivity were measured in a walk-in anechoic chamber. Compared with previous fly-inspired microphones, the presented prototype is the first with three measurands (p0, dp/dx, and dp/dy) derived simultaneously from a single diaphragm.