We have all seen sound waves visualized on oscilloscope or even spectrum analyzer screens, but how often have we seen actual photographs, or even better video, of the three dimensional compression and rarefaction that is sound propagating in the real world?
NPR’s skunk bear has a great video both demonstrating and explaining Schlieman flow visualization of actual sound waves as captured by high speed camera. You can see the tremendous compression caused by a stack of books falling or the much weaker wave caused by a hand clap.
