Cymatics van Nigel Stanford.

Cymatics (from Greek: κῦμα “wave”) is the study of visible sound co vibration, a subset of modal phenomena. 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.[1] Different patterns emerge in the excitatory medium depending on the geometry of the plate and the driving frequency.

Van Nigel Stanford.