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. Here's what it looks like as a longitudinal wave.

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.