Singing Sand Dunes

I find this to be fascinating. I had no idea that sand dunes made sounds, let alone musical tones!

clipped from dsc.discovery.com When Sand Dunes Go Boom The age-old mystery of why the dunes of 30 or so sand fields worldwide make eerie booming and singing sounds may be solved. the deep tones made by the 30 or so singing dunes worldwide aren't very different from those made by a stringed instrument. "We've been sliding down dunes and the whole thing is vibrating," she said. Audio analyses of the dune noises show a surprisingly pure tone. "It looks right on — you even get the harmonics just like you do with a [cello] string." It's as if there is some sort of "waveguide," like a giant string, in the dune that favors only certain frequencies of sound. That waveguide, it turns out, really exists. It's on the slip-face of the dunes — that's the steep side facing away from the prevailing wind. "The sand moving down the face is the moving string, but it's really playing the whole body," Hunt told Discovery News. clipped from dsc.discovery.com Hunt's team has come up with a recipe for singing dunes: they must be big, dry and dense.