Measurement of the correlation properties of thermal acoustic radiation

The space correlation function of sound pressures produced by a source of t hermal acoustic radiation in the megahertz frequency range is measured by a system of two plane piezoelectric transducers. The source of radiation is an acoustic blackbody radiator represented by a heated strip of material wi th a large absorption coefficient. The strip is moved along the coordinate x perpendicular to the acoustic axis of the system. The correlated signal p eriodically varies in the course of the strip motion, and its magnitude is proportional to the difference between the temperatures of the source and t he surrounding medium. The space correlation function R(x) is calculated, a nd the results of the calculation agree well with the experimental data. Th e problem of the development of a device for correlated signal measurements in passive thermoacoustic tomography is discussed. (C) 2000 MAIK "Nauka/In terperiodica".