Suspended metal wire array as a thermoacoustic sound source

Abstract

We demonstrate that a suspended metal wire array can be used to produce high-pressure sound waves over a wide spectrum using the thermoacoustic effect. We fabricated air-bridge arrays containing up to 2×105 wires covering an area of a few square centimeters. The supporting silicon wafer was isotropically plasma etched to release the wires thereby avoiding heat contact with the substrate. Sound pressure levels reaching 110 dB at a distance of 8 cm were demonstrated near 40 kHz in free field. The devices are also able to reproduce music and speech. They have potential for applications especially in the ultrasound range.