Singing Tube
A Singing Tube is a
phenomenon in which
sound is produced by placing a
bunsen flame inside a tube.
The varying pressure waves inside the tube set up
compressions and
rarefractions that rapidly
oscillate. This occurs because the pressure variances travel vertically up the tube and then reflect due to the
end effect of the tube and re-enter the tube now travelling downwards. The up-wave and down-wave combine to form a pattern. If the
pressure waves are of the right
frequency they assume the pattern of a
standing wave. This "
stationary" wave generates a
frequency much higher than a normal pressure wave.
Prediction of the frequency emitted is difficult because many standing waves are formed (
fundamentals, and subsequent
harmonics) simultaneously.
The composition of the tube has no effect on the sound because it is the collumn of air - not the tube - that is vibrating. The effect can also be achieved by heating high resistance
gauze using
direct current or by a heated wire mesh placed internally.