What Does Sound Look Like?

 What do you find interesting about this video? How does seeing sound visualized help you understand what sound is?

What I find so interesting about this video, is the fact that you can actually see sound, and a change in air density using a high speed camera and Schlieren Visualization. You can also see any change in air density, including the heat off of a human hand! It helped me understand what sound is because you can actually see it, and see how it could translate into sound waves.