By adapting F. A. Angona's [J. Acoust. Soc. Am.25, 1111 (1953)] construction to H. Oberst's [Akust. Z.2, 76 (1937)] method—essentially the Kundt's tube—resonance tubes have been constructed that are capable of going to several hundred atmospheres of pressure at 300°C. The tubes are, conveniently, about 2 ft long with a fundamental frequency of 250 to 300 cps, depending on the gas. By casting the basic tube in a lead or die‐casting alloy jacket the annoying mechanical vibrations of the tubes are suppressed or moved to high frequencies above the region of interest—500 to 10 000 cps. The plane modes are used exclusively, from the 2nd to the 20th harmonic, though the 55th and higher can be recognized and measured. The width of the resonances at the 3 db points is proportional to the absorption, after allowance for the tube effect (Kirchhoff). Relative velocity can, of course, be measured accurately also. The work of H. and L. Knötzel [Ann. Physik2, 393 (1948)] with oxygen has been repeated to test the method, and their results are completely confirmed both as to magnitude of the absorption and the value of the relaxation time. It is intended shortly to apply this method to nitrogen at high temperatures. A minimumf/pof perhaps 1 cps‐atm should be attainable. (Work supported by the Office of Naval Research.)