Shaking Sands

screen shot/youtube.com/brusspup

Sand on a vibrating plate. The translation of the text is "When one makes a plate vibrate at certain frequencies, the particles, such as sand, that are on top arrange into forms that become more and more complicated as the frequency increases. This property was discovered by Ernst Chladni in 1807 when he used a bow to make a copper plate vibrate, [and so] these forms are known as the 'Chladni acoustic figures'" (videos; N.B., the caption above the second video reads "The same video with original sound; consider lowering the volume"!): http://www.laboiteverte.fr/du-sable-sur-une-plaque-vibrante/