Quantitative measurement of acoustic whistlers

We present an experimental setup capable of quantitative examination of acoustic whistlers in tubes of varying lengths and diameters. It is simple enough to be used as an undergraduate lab or classroom demonstration. The setup can be used to show the transverse modes of a cavity, and the difference between the group and phase velocity of a wave. It can also be used to determine the velocity of sound to an accuracy of 3%. We present the results of several experiments used to determine the acoustic modes present in transient whistlers. Our results differ significantly from a "geometrical acoustics" derivation of the acoustic whistler made in an earlier paper. (C) 1998 American Association of Physics Teachers.