Oscillations and Waves > Instruments > Air Columns DCS# 3D30.21

DISPLACEMENT NODES AND ANTINODES IN CONICAL RESONATORS


APPARATUS
brass phonograph horn 202-07-C
HP audio generator 202-08-G
speaker on a tube 202-06-D


DESCRIPTION
Move a speaker on a long tube along the axis of the cone.

Set the function generator at some high harmonic (2 kHz) of the fundamental (200 Hz) of the resonator.  Then there will be many wavelengths inside the cone.  As the speaker is pushed further into cone you will hear frequent alternations of high and low intensity sound, according to whether the speaker is near an antinode or a node of displacement.  I.e., you can only excite a mode near one of its antinodes.  Alternately, you can view it as an interference phenomenon, which is what standing waves are.
-REW
NOTES

See also: Resonant Frequencies of Cones

REFERENCE

Sutton S-114.