Chladni plates refer to a vibrating plate onto which fine particles like tea, sand or salt are placed. The plate is then vibrated by a speaker directly coupled to the plate. Invented by Physicist and musician Chladni
Depending on the frequency of the sound and the shape of the Chladni plate geometric patterns are formed. The particles come to rest in sound waves nodes to make these patterns. The patterns are from standing waves created in the plates based on the excitation and reflections of sound.
Old school Chladni plates were often excited by running a violin bow along the edge of them, but with a speaker you can deliver precise frequency of sound and at much higher amplitudes. Luthiers use these to tune the plates of violins to get them sounding just right – though I am yet to do something more adventurous than tap tones.
The examples below are for a STEM science trip on the Maths of music and motion see stem-fit.com. The setup has been made to be portable so its a smallish speaker, battery powered (courtesy of a power drill) and a circular plate (you get nice annular symmetry of the patterns, one of a violin to show some of the complexity there.
For this trip as my wife Charlie is also talking about ear biology and hearing, so I have also made a liner model to represent the cochlear (if it was unrolled) and kids are asked to imagine them as the little hairs in their ears. Education about the ear is particularly important outback as almost half of indigenous children have hearing loss owing to a particular infection that spreads in their communities. So a bit of fun really engages the learning aspects of it as well.
Just for fun we are not only putting pure tones through the plates, but also Beethovens 5th and my son plans to whip out his electric violin as well…sliding around to find resonant frequencies doesn’t quite count as violin practice though dude!.
