I don't know why this video is spooky, but it certainly is. A guy tips a load of rice over a panel which is vibrating at various audio frequencies. The rice arranges itself into patterns depending on the frequency. Wooooh! (Thanks Mikey). If you're freaked out by that, try this!
Posted by Tom Whitwell.
Rice? Or white sand or salt?
Science museums have a variation on this where square, triangular and circular metal plates are mounted. Pour the white sand onto a plate and set the plate vibrating with a large bow (like a violin bow, but more industrial sized) to see how the vibrations and shape of the plate interact with the sand.
This is the coolest tho', driving the plate with an oscillator. Thanks again, Music Thing. (As for the truly spooky rendition of "Roundabout" . . .)
God bless Music thing... creepy rice/salt pattern videos, and a truly horrendous Roundabout version...
surfing through the related You Tube vids I came upon this, which is almost creepier...http://www.youtube.com/watch?v=fmGmsjvq5cM&search=showchoir%20riverside%20show%20YES%20roundabout%20choir%20hastings%20music%20fun%20dancing%20singing
I wonder how it would look with for instance a square or sawtooth waveform. Or two notes at different musical intervals (I bet the pattern would get gradually more complex from an octave (1:2) to a fifth (3:2) and so on down to a diminished fifth (64:45))
You can set up more complex patterns on the plates by putting your finger on the edge of the plate at an integral fraction along the length (ie. 1/2, 1/3, 1/4 the length of the plate). This creates a node and forces higher order standing waves to be set up. Directly analagous to playing harmonics on the guitar.
I've been doing some experiments since reading this post. Try placing a speaker on its back and placing a dish on top of it. I've discovered interesting results with mild sprinklings of sand, flour, sugar and so on. Nothing really like the cornstarch fingers, but I've made a big mess now and I feel happier.
In theory most speakers can produce the accelerations used in the cornstarch video, but I think you'd need to glue the dish to the speaker cone to get the downward acceleration.