Standing Waves: A tube closed at one end

For a tube closed at one end, the resonant standing waves have a node for displacement at the closed end (no motion there) and an anti-node at the open end. Once again, the pressure change is 90° out of phase with the displacement, so there's no change from atmospheric pressure at the open end and the pressure fluctuations have maximum amplitude at the closed end.






Fundamental x _:

To satisfy these conditions the relationship between the wavelengths of the resonant standing waves and the length of the tube is:

nλ/4 = L, where n = 1, 3, 5 ...

Note that only the odd harmonics satisfy the conditions for resonance.

The resonant frequencies for the tube closed at one end are then given by:

f = nv/4L, where n = 1, 3, 5, ...

Many musical instruments are essentially tubes with one end open and one end closed.