Natural vibration figures of plates
To me it is interesting and I am fascinated by generating figures with sound and natural vibrations.
They called Chladni figures and are connected with the superposition of waves and the resulting interferences.
The figures are occur if a thin metal plate is sanded and at one edge with a violin bow are generated vibrations. From that edge the vibration spreads out as a wave in the plate. At the edges of the plate the wave is reflected and inside the plate thus the original and the reflected wave are superimpose each other. Thus a standing wave is formed whereupon the sand is moving away from the intense vibrating areas to the positions where the plate is vibrating less or is motionless. Patterns in the sand are occur, which show us the node lines of the standing wave and thus the apparent static points of the plate, where the vibration amplitudes mutually are minimizing each other or totally extinguishing each other.
The optimization of musical instruments is one application of Chladni figures. Fascinating issues connected with interference are i.e. anti-sound, which reduces disturbing noise, interferometer, which are using interference effects for the measurement of lengths or phase shifts, up to interference in the quantum mechanics, where particles are behave like waves and therefore also interfere.
The pictures and the video show Chladni figures, generated with sand on a metal plate and a violin bow.