This study of the velocity of high frequency sound in small tubes covers the range of frequency from about 10 to 80 kilocycles per second, and in diameter from 1/2″ to 3/16″. The method of G. W. Pierce, using magnetostriction oscillators, has been followed, providing high accuracy of measurement. Careful precautions in the construction were taken to eliminate the variations due to humidity, impurity, and to spurious reflections. The results tend to support definitely the Helmholtz‐Kirchhoff reduction law, but provide a smaller observed value of the constant for pure air compared to the theoretical value. The value of free space velocity derived from these experiments checks that independently obtained by Grabau, using a similar method in air, to within 1 part in 4000. Hence the present tube method may be applied to delicate measurements of sound dispersion in pure gases, and their mixtures.