Glass tube for demonstrating standing sound waves and calculating wavelengths of sound using cork powder in a method devised by Kundt.
Cork powder is spread evenly throughout the tube by means of a filler chute. Then a sound source, e.g. a whistle, a 1 700 Hz tuning fork (U10115) or a horn speaker (U8432680), is used to excite the powder into a regular pattern of nodes and antinodes. The effective length of the tube can be altered by means of a piston.