SOUND VELOCITY AND ABSORPTION IN LOW-PRESSURE GASES CONFINED TO TUBES OF CIRCULAR CROSS SECTION

The propagation constant for sound waves propagated through gases confined to tubes is shown to be a function of the specific heat of the gas, a “Reynolds” number, a “Knudsen” number, and the momentum and energy accommodation coefficients of the surface. A numerical solution for the propagation constant agrees with room temperature velocity and absorption measurements in Ar and N2 assuming a momentum accommodation coefficient of 1 and an energy accommodation coefficient of 0.9. No effort was made to clean the tube wall surface, and no difference could be detected in a stainless steel and a brass tube. The method offers considerable promise for measuring energy accommodation coefficients. © 1969, Acoustical Society of America. All rights reserved.