Ultrasound radiation from simple thermoacoustic transducers

Abstract

Thermoacoustic equations are derived to describe the sound pressure radiation by a heated plane over a material substrate. By determining the velocity of an equivalent piston, the sound pressure emitted by a thermoacoustic source of finite dimensions can be calculated at any frequency. The measured sound pressures, obtained with devices constructed ad hoc for the experiments, are in good agreement with the theoretical expectations in the audio and ultrasound region, from 500 Hz to at least 100 kHz. The main results show that it is possible to produce significant sound pressure radiation in this frequency bandwidth with very simple devices, constructed with common materials. A potential feature for the kind of sound source described in this paper is that their radiating surfaces can have a desired shape, not only a plane one.