Velocity and Absorption Measurements at Supersonic Frequencies

Abstract

Importance of Supersonics. This field is related in varying degrees to gas theory, thermodynamics, chemistry, physical chemistry, mechanics, heat, radio engineering, navigation and biology. The author's work in this field began in 1919 and has been confined to a search for a suitable high-frequency source and to the measurement of velocity and absorption in air, in oxygen and in carbon dioxide. Quartz slabs, properly cut from the original crystal and sputtered on both faces with metal were found far superior to the other tested sources for measurements requiring constant frequency and intensity. With such crystals, there were obtained frequencies ranging from 300 to 2000 k.c. The velocity in air was found to be approximately 331.6 m/sec. in this range. At the lower frequencies the absorption appeared to exceed that predicted by the earlier theory. No serious deviation from expected values were found in oxygen. With carbon dioxide the velocity was found to increase about 3 percent from 300 to 2000 k.c. The absorption greatly exceeds the values predicted by the earlier theory. Both velocity and absorption values are in good agreement with those obtained theoretically by Kneser.