An Air-Coupled Electrostatic Ultrasound Transducer Using a MEMS Microphone Architecture

We demonstrate the transmission of ultrasound in air using a device that resembles a MEMS microphone in its construction. The device has a 1 mm diameter diaphragm and uses a perforated backplate for electrostatic actuation. The device is driven with large amplitude AC signals, with peak values that exceed the pull-in voltage of the diaphragm. In doing so, relatively large diaphragm displacements are achieved, as the diaphragm oscillations traverse the complete diaphragm-backplate gap. Large amplitude diaphragm vibration is advantageous for high SPL applications in air, as sound pressure is directly proportional to diaphragm displacement for a given operating frequency. Transient diaphragm displacement waveforms are measured in response to tone-burst waveforms ranging in frequency from 4 kHz to 97 kHz. Resultant acoustic pressure waveforms in air are made using a broadband microphone. [2022-0082]