Recent Progress in Supersonics

Abstract

A summary of recent contributions to several branches of acoustics which have been useful to physics and to chemistry. The theory of the propagation of sound in dispersive gases is first discussed from a standpoint which it is hoped may be intelligible to those who have no special knowledge of the subject. There follows a description of the various types of apparatus which have been devised to measure the velocity of sound and the attenuation coefficient. The direct photography of sound using Töpler's “Schlieren-methode” is stressed as promising to obviate difficulties inherent in the interferometric technique. The experimental results are then summarized with particular attention to the effects of pressure, temperature, and traces of foreign substances on the dispersive behavior of gases. The collision theory has received strong support from the majority of these measurements. Finally, the effects of intense sonic and supersonic radiation are briefly reviewed. Since most of these have been found to depend upon cavitation, the role of cavitation is examined. A ballo-electrical explanation of the phenomena is considered the most promising, although it is difficult to prove.