Measurements of sound propagation in narrow tubes

The propagation of sound in hollow tubes is a fundamental theme common to many areas of classical acoustics. Kirchhoff's theory explaining the propagation of sound in a circular tube is now playing an important role as a starting point in studying sound in porous media. This paper reports on measurements of the phase velocity and attenuation coefficient in the narrow regions of tubes, where the sound undergoes anomalous dispersion and is seen to slow down remarkably to the extent that a runner can pass ahead of it. Kirchhoff's theory can be verified by experiment over a wide range of thermodynamical conditions, from isentropic to isothermal.