Propagation of Sound in Critical Binary Liquid Mixtures near the Critical Point

Abstract

It is well known that very large attenuation of sound is produced in critical binary liquid mixtures as the critical temperature is approached, but there is disagreement whether this large attenuation is due to scattering or to true absorption. We have scanned the radiation emanating from a scattering cell containing a binary liquid mixture at several closely spaced temperatures near the critical temperature. Whereas there is a very large drop in the strength of signal at zero bearing angle, there is no consequent rise at any other angle, as there is in the case of true scattering (e.g., as has been experimentally found in scattering from air bubbles.). We conclude that the attenuation measured by previous observers should be assigned primarily to true absorption, and that the effect due to scattering is negligible. [Work supported by the Office of Naval Research, Acoustics Branch.]