QUANTITATIVE MEASUREMENT OF ACOUSTIC WHISTLERS

We present an experimental setup capable of quantitative examination o f acoustic whistlers in tubes of varying lengths and diameters. It is simple enough to be used as an undergraduate lab or classroom demonstr ation. 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 t he acoustic modes present in transient whistlers. Our results differ s ignificantly from a ''geometrical acoustics'' derivation of the acoust ic whistler made in an earlier paper. (C) 1998 American Association of Physics Teachers.