In the dark hours of early morning, before the scorching heat arrived, Melany Hunt and her research team climbed massive sand dunes this summer in Death Valley and the Mojave Desert.
With heavy equipment in tow, they listened for sounds beneath the billions of granules—an acoustic stirring that observers have noted for centuries.
In order to hear the low-frequency booming sound, be sure to use headphones or speakers with bass:
The team investigated the characteristics of waves emitted during what are known as burping and booming emissions. Their findings appear in a paper published this week in the journal Physics of Fluids.
Booming sand dunes produce a persistent, low-frequency sound that resembles a pure note from a musical instrument. Prior to the onset of booming, the emission consists of short bursts or burps of sound of smaller amplitudes.
The researchers discovered that the surface and volumetric signals are present but with distinct features and properties. To their surprise, Hunt and her colleagues also learned that by providing an impulse on the surface of the massive mound of sand—a simple hammer blow on a plate, for example—they could trigger the natural resonance within the dune.
“We had never before observed this in the literature,” says Hunt, a professor of mechanical engineering at Caltech.