A similar thing happens for a tube open at both ends, in that reflections of the sound at both ends produces a large-amplitude wave for particular resonance frequencies. For the standing waves, an open end is an anti-node (maximum amplitude point) for displacement.

The pressure change in a sound wave is 90° out of phase with the displacement. The simulation shows a representation of the displacement - the pressure change would have nodes where the displacement has anti-nodes, and vice versa.

In addition, the simulation shows a transverse wave - a sound wave is, of course, longitudinal. It's just easier to represent it as transverse.

The resonant frequencies for the tube open at both ends follow the same equation we had for the string fixed at both ends:

fn

=

n v 2L

, where n = 1, 2, 3, ...

Many musical instruments are essentially tubes open at both ends. As with strings, the sound heard when the instrument is played is a particular combination of the fundamental frequency and different harmonics.