Harmonics - Salt on a vibrating table

if I were to guess, I would say that those shapes are caused less by the resonance pattern of the salt crystals, and more the table/metal itself.

What happened at 2:04? Did the speaker just blew up?

Everything is vibrating from low to high frequencies....light being out of our hearing range, but in our visual....or at least some.... until it becomes radio, X ray, and gamma waves... this is a great visual representation of a sound wave by product.... and somehow makes me feel happier about science more so than religion because this is actually beautiful!

That'll be 'Bi-product' ...Oooorrrps!

It is easier to see with one dimensional waves on a string first. The nodes are the places where the string never moves. Apply it to the two dimensional sheet metal and the salt settles in the nodes. Only certain frequencies can create a standing wave which is why it changes from one pattern to another quickly. Also, waves apply to everything in the universe which is why improperly designed buildings and bridges break in the wind

Not people of all ages are able to hear the higher frequencies. When you get older the ability to hear high pitched notes diminishes. Baby's can even hear dogwhistles.

fractal and second symmetic

It reminds me of those absurd crop circles.

Its a 2-dimensional example of why atomic orbitals exist. Everything is waves.

fractals....