Sound Radiation from Thermal Non-resonant Sources: Planar and Nonplanar Geometries

An acoustic source that radiates sound in the audible and ultrasonic regions, to at least 100 kHz, has been under development. These kinds of sources are very simple and easy to construct; they consist of a heated surface over a material substrate. Moreover, they have additional advantages: they can be made with plane, convex or concave radiation surfaces, and they have no resonances. We present, as examples of actual sources, a cylindrical source and a baffled rectangular piston. A comparison of the measured sound pressures with those calculated from theory, for the two examples, shows a very good agreement.