Sand patterns formed from vibrating a square sheet of thin metal. These formations, known as Chladni patterns, occur when fine particles, such as grains of sand or salt, form a unique pattern in response to pure tone vibrations such as musical notes. This sand was placed on a metal plate that was vibrated at different frequencies. When the plate is driven at a resonate frequency the sand grains will collect in the nodes. Chladni Oscillations are a standing wave pattern visualized by vibrating a metal plate. The nodes and anti-nodes of the oscillation are made visible by placing sand grains on the plate. This technique for visualizing sound waves was discovered by Ernst Florens Friedrich Chladni (1756 ? 1827) also know for his work with the speed of sound.