School of Physics Lecture Demonstration Manual

Wg-3 Knipp's Singing Tubes

Published: Wednesday 15 March 2006 - Updated: Thursday 31 March 2011


To demonstrate the conversion of thermal energy to sound and the phenomenon of beats.



Click on pictures to enlarge.

Knipp's Singing Tube Diagram


The tubes are constructed such that each contains a smaller diameter tube closed at one end and held fixed by glass studs. The physics of a Knipp's tube is similar to that of a closed organ pipe. When heat is applied as shown in diagram the air will vibrate along the entire length of the tubes. Heated air will move into the smaller diameter tube increasing the pressure there. This action reinforces the longitudinal vibrations until a sound is audible. The combined length of the large and small tubes add up to one quarter wavelength of the sound generated. In addition one of the tubes has a variable length so that the fundamental may be varied and produce beats.

Safety notes

Sharps safety 

Fire/Burn safety 


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