What Does Sound Look Like? NPR’s SkunkBear shows us the differences in fluid densities — in the form of compression waves in a gas, the air that surrounds us — thanks to the light passing through those fluids. Schlieren flow visualization and a high speed video camera make it possible.
When light travels through areas of different air density, it bends. You’ve probably noticed the way distant pavement seems to shimmer on a hot day, or the way stars appear to twinkle. You’re seeing light that has been distorted as it passes through varying air densities, which are in turn created by varying temperatures and pressures.
Schlieren Flow Visualization can be used to visually capture these changes in density: the rising heat from a candle, the turbulence around an airplane wing, the plume of a sneeze … even sound.