I had no idea that sand made these kinds of sounds.
"Singing sand dunes" of the Gobi Desert. A royalty-free image from corbis.com.
There is a seven second audio in mp3, Real Audio, or for Windows Media Player along with an article about the composition of these sand dunes at Nova: Booming Sands: Recipe for Noisy Sands. The booming sands audio (the second one; first is croaking sand) and the idea that sand could make sound like musical instruments, is fascinating.
"When he heard them in the Gobi Desert, Marco Polo believed they were spirit voices. Ancient Chinese literature describes ritual celebrations of their divine power. In 1941, after crossing the Sahara, British engineer and explorer R. A. Bagnold was captivated by their spell. The "weird chorus" of sound-emitting desert sands was, he wrote, "the song of sirens who lure travelers to a waterless doom, the toiling of underground bells in sand-engulfed monasteries."
After generations of mystical interpretations, researchers are finally closing in on a scientific explanation for the acoustics of sand. They now agree that the phenomenon of noisemaking sand is made possible by the action of displacement, which produces musical instrument-like vibrations in sand grains. The exact recipe for noisy sands is ..."
Photo above and NASA article on city swallowing and singing sand dunes- here.