New Phenonema in a Sounding Dust Tube

Abstract

WITH the view of making accurate measurements of the velocity of sound, and hence of the ratio of the two principal specific heats of gases, we have been studying the formation of dust figures in a sounding tube. Instead of using a stroked rod to produce the vibrations of known frequency, as Kundt did in the form of experiment known by his name, we employ a telephone diaphragm (actually a loud-speaker unit) excited by a current of approximately pure sine-wave form, which is produced by a suitable valve circuit. The frequency of the vibration is then varied until one of the resonant frequencies of the tube is reached, when the dust phenomena are produced with great distinctness and can be studied at leisure.