Today, we know that sound travels in waves through solid, liquid, and gas, but we didn’t always know. In the late 1700s, one man was the first to show that sound travels via waves by creating a way to visualize the vibrations: Ernst Chladni (1756-1827).
Born in Germany, Chladni was a Hungarian physicist and musician who did a lot of early work in acoustics and the study of meteorites. Because his father was a lawyer, he was pressured to pursue a career in law. After obtaining a law degree, he wanted to change careers and study physics. However, his father disapproved of his interest in science, and forced him into law school. Shortly after Chladni graduated from law school in 1782, his father passed away. This was no doubt a hard time for Chladni, but it ultimately left him free to study physics like he wanted to.
In 1794, Chladni published his idea that meteorites came from outer space. At the time, he was ridiculed – most people thought that meteorites came from volcanoes. Luckily, he was proven right ten years later after a giant meteor shower devastated a small French town. Chladni also paved the way for experimental acoustics. Because he was interested and talented in music, he invented instruments based on previous inventions by Benjamin Franklin and Robert Hooke, like the euphone and clavicylinder. Additionally, he determined the velocity of sounds in gases using an organ pipe. Chladni then went on to develop Chladni’s law: a formula that relates the
frequency of modes of vibration for a flat circular plate. This can be used to predict patterns of vibration on flat surfaces and describe the vibration of cymbals and bells.
However, Chladni is most well known for the development of Chladni figures. Chladni was actually building on earlier experiments by Robert Hooke, who did something similar by observing nodal patterns in glass plates in 1680. By vibrating a flat surface that is secured in the center and pouring salt or sand on top, complex patterns can be revealed. Playing a tone to vibrate a plate will cause areas of no vibration, which are called nodal lines. As the vibration continues, the salt or sand will move away from the antinodes (areas where the amplitude of the standing wave is at its maximum), concentrating along the nodal lines where there is no
vibration, thus outlining the nodal lines. As the pitch of the tone is increased, more complex patterns are created. Different shapes of plates will produce different patterns. You can also draw a violin bow across the side of the plate until it reaches resonance, which will create the same effect. Chladni figures are incredibly complex, and have a lot to do with very complicated math and physics concepts.
You can view a demonstration here.
You can also find tutorials on creating your own Chladni plate, and if you can stand the sound, you can discover some pretty interesting patterns! If you don’t want to make your own, you can always find a Chladni figure generator or buy a kit online.
