Altyn-Emel National Park & the Singing Dunes

The sound is real and it surprises people — a low organ-like drone or a distant propeller, loud enough to feel in your chest when a big enough slab of sand lets go. It happens because the dune's sand is unusually uniform: grains of almost identical size, rounded and polished by wind, and completely dry. When a layer avalanches down the slip face, the grains shear past each other in step rather than at random, and the whole moving sheet vibrates at one frequency. The body of the dune underneath acts as the resonating chamber, the way a guitar body does.

Two conditions have to hold. The sand must be bone dry, so after rain the dune stays silent for a day or two. And enough sand has to move at once, which is why the drone usually needs either a strong dry wind or a person sliding down the crest to set it off. Late morning to mid-afternoon on a dry, breezy day is the reliable window; still, damp mornings are the usual reason visitors leave disappointed.

The dune sits between the Ulken and Kishi Kalkan ridges, and unusually it does not migrate — opposing winds funnelled between the two ranges hold it in place, which is why it has stayed put for thousands of years while its sand is constantly rearranged.