Abstract
A calculation is given of the temperature gradient set up when a sound wave is absorbed in a dielectric medium at low temperatures, due to the increase in the `crystal momentum' of the thermal phonons. Two expressions are obtained, one for the case where momentum conserving phonon-phonon collisions predominate, and the other for the case where momentum destroying collisions are in the majority. Numerical results are given for quartz, where it is found that the effect is probably too small to be measured by current techniques.