taken from yahoo answers:
The result is that one end always has a node and the other an antinode, whether we refer to displacement or pressure. In any standing wave, a node is are separated from the nearest antinode by 1/4 wavelength or 90 deg of phase. Thus the longest standing wave length (fundamental) that can exist in the closed-open pipe is 4L. With 1/2, or 1.5, 2.5 etc. wavelength separation of the pipe ends you can't have a node at one end and an antinode at the other, but with 1/4, 3/4 etc. separation you can. This means the open-closed pipe supports odd harmonics of the fundamental but not even ones.
seems legit.
