You can take pictures of what you see, but what about what you hear? It is possible, using a photography trick that can make sound visible.

It's called Schlieren Flow Visualization, and it can be used to watch any changes of density in the air, including those caused by heat. But it's an especially cool visual when you see it working with sound.

So, how does it work? Adam Cole, who runs NPR's skunkbear tumblr, put together this video explaining how combining two mirrors, a light source, a barrier, and a camera yields the effect by deflecting light of its path in a way that produces darkening around the changes in density. This set-up allows you to actually see the sounds in the video of everything from someone clapping, a firing AK-47 (GIFed above), or even a lit firework (below).


Of course, it's not just a cool trick — it's also scientifically useful. Epidemiologists, for instance, can use also use it to study coughs and, before wind tunnels became commonly used, it allowed scientists get a better look at just what was happening with flowing air.

Check out the full video here, and tell us what sounds you'd most like to see in the comments.


Images via Adam Cole / Skunkbear - NPR.