CYMATICS

The study of wave phenomena, especially sound, and their visual representations is called cymatics. 

The name was coined by the Swiss physician Hans Jenny. 

Typically the surface of a plate, diaphragm, or membrane is vibrated, and regions of maximum and minimum displacement are made visible in a thin coating of particles, paste, or liquid. Different patterns emerge in the excitatory medium depending on the geometry of the plate and the driving frequency.

The apparatus employed can be simple, such as the Chinese spouting bowl, in which copper handles are rubbed and cause the copper bottom elements to vibrate. Other examples include the Chladni Plate and the so-called cymascope.

On July 8, 1680, Robert Hooke was able to see the nodal patterns associated with the modes of vibration of glass plates. Hooke ran a bow along the edge of a glass plate covered with flour, and saw the nodal patterns emerge. 

At different frequencies of sound, different substances create different nodal patterns. Increasing frequency creates more complex nodal and geometrical shapes and patterns.

Picture credit: Wikipedia