Dispersion and Absorption of High Frequency Sound Waves

The absorption of sound waves in gases had been explained heretofore by friction and heat conduction. A third factor is here introduced, namely, the slow rate of exchange of energy between the translational movement and the internal degrees of freedom of the molecules. The formulas determining the absorption and dispersion of sound waves, due to these three effects, are developed. Comparison with the experimental data available shows that the new effect is either of considerable influence or even predominant. The rate of exchange can be calculated.