Some visitors go to Kazakhstan's Altyn-Emel National Park—a preserve the CBC says is four times the size of Hong Kong—to view ancient burial sites or catch a glimpse of wildlife; others go to listen to the park's famous singing dune. The nearly 500-foot-high pile of sand, which stretches for about 2 miles, is tucked away in the Tian Shan mountain range near China's border, Reuters notes, and when the weather is especially arid, visitors can hear a sound that some compare to an organ. The dune's melodious moaning can be set off by wind or when the sand is disrupted by people: In a YouTube video of one family wanting to demonstrate the desert chant, you can hear the ominous sound (when the father isn't yelling at his kids to keep quiet). But while the strange symphony used to be attributed to rumors such as Genghis Khan being entombed underneath it, scientists have come up with a more likely explanation—for this dune, and for the many others like it around the world.
The "booming and burping" sounds, as Live Science puts it, are caused by varying sound waves moving within the dune, per a 2015 study in Physics of Fluid. By analyzing the sounds that moved through similar dunes in Death Valley and the Mojave Desert, the researchers found that the way grains of sand rubbed against each other produced the mystery tune. "Booming sand dunes are able to produce a persistent, low-frequency sound that resembles a pure note from a music instrument," Nathalie Vriend, the study's lead researcher, tells Live Science, even pinpointing the note to "a dominant audible frequency between a D and G sharp in the second octave below middle C, and several higher harmonics that may be heard from distances far away and may last for minutes." Vriend adds that just a bit of movement is all it takes to trigger the very noticeable lowing. "It is really difficult to comprehend that such a small and thin avalanche creates such a loud sound that booms over the desert floor," she notes. (In Oregon's dunes: a shipwreck.)