Chladni plate constructionChladni 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. Depending on the frequency of the sound and the shape of the 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.
The examples below are for my wife's STEM science trip on the Maths of music and motion to the Northern Territory communities. The setup has been made to be portable so its a smallish speaker (I used a car speaker), an ebay audio amplifier module, some gluing of a 50mm PVC conduit onto the speaker it to make a housing for the plates to be mounted. Its battery powered (courtesy of an Ozito power drill) and reversing the charger mounting clip.
Symmetry of 440Hz (concert pitch A) on a circular Chladni plate 
440Hz on a violin shaped plate
With a circular plate you get nice annular symmetry of the patterns, and one of a violin to show some of the complexity there.
For this trip as my wife Charlie is also talking about hearing 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 using an audio generator (a computer or smart phone APP) , but also Beethovens 5th and direct feed in from an electric violin to add to the fun for musicians. I'd include some videos of all the salt particles jumping around if i could...its really engaging from an educational point of view.
Teaching for a resonant frequency using an electric violin as an input source
Resonance on the Chladni plate using a violin as a source (violins generate many complex harmonics)
