I’ve posted some interesting ways to actually physically see sound waves in the past, but here’s more scientific way done in a lab. The following videos are from the Naval Postgraduate Physics Department’s YouTube channel, which is dedicated to showing physics experiments. That’s cool enough by itself, but what’s even better is that a large number of these experiments are dedicated to audio topics, so it’s a great way to really understand the physics of sound from something other than a book.
In this case it’s an experiment built around a Helmholtz resonator tube filled with sawdust that illustrates not only harmonics, but wavelengths as well, two things that are important to every day recording life.
There are two videos (parts 1 and 2) that provide an excellent visual example of harmonic concepts. These videos aren’t too long, and are an easy view. That being said, here’s a great little Chrome plugin that I use all the time to speed up videos called Video Screen Controller. It helps you to get to the point just that much faster.