Chladni was an 18th century musician and physicist who was instrumental in the development of acoustics, which is the science of sound. Sound is made of physical vibration. He found a very interesting way to demonstrate the physical qualities of sound—by drawing a violin bow across a plate sprinkled with sand, he produced patterns and shapes that are now known as Chladni patterns (or figures).
The science of the visualization of waves, particularly sound waves, has come to be known as cymatics, a term coined by Swiss scientist Hans Jenny (1904-1972). Jenny conducted a wide range of experiments with the way that sound affects different substances, and was able to produce Chladni patterns by using oscillators and even the human voice.