In Did you Know? the National Geographic magazine team shares extra information we gathered to expand your knowledge of our featured subjects.
Some hills are truly alive with the sound of music. In about 30 known places around the world, sand dunes produce low, haunting notes that carry for miles. Coming from "booming" or "singing" dunes, the notes are produced when a thin sheet of sand avalanches down the face of a dune. The avalanches can be created by wind or natural slumping, or by people sliding down a dune. The avalanches cause shearing of the sand grains, whose motion produces wavelengths of sound that resonate and build up into a low-frequency, steady musical tone (dunes sing in a range about two octaves below that of middle C).
However, dunes don't boom with every avalanche; many factors have to coincide to make sand sing. The dunes only sing in hot and dry weather when they have a layer of dry, loose sand on top of a stationary, more compact layer that acts as a sound board to reflect sound waves; moisture silences the dunes. Further, the sand grains need to be well-rounded, smooth, and approximately the same size to resonate at the same frequency.
You can visit these booming dunes in the American Southwest:
Eureka Dunes, Death Valley National Park, California
Kelso Dunes, Mojave National Preserve, California
Dumont Dunes, Mojave Desert, California
Sand Mountain, Nevada
Big Dune, Amargosa Desert, Nevada
Great Sand Dunes National Park and Preserve, Colorado