The Songs Of Two Sand Dunes

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Description

These two sand dunes both "sing" when sand rolls down their sides. But they sing quite differently.

Sand dunes only sing in a few areas across the globe, and their songs – always a low, droning sound — have been an object of curiosity for centuries. Marco Polo encountered their haunting drone during his travels and Charles Darwin, in his book “The Voyage of the Beagle,” wrote of testimonials from Chileans about the sound of a sandy hill they called the “bellower.”

The song of the sands is a low hum at a frequency within the bottom half of a cello’s musical range. These dunes only sing when the sand is sliding down their sides. People can set the sand in motion themselves or, more eerily, the wind can create sand avalanches, creating a sudden, booming chorus.

Physicist Simon Dagois-Bohy and his fellow researchers at Paris Diderot University in France recorded two different dunes: one near Tarfaya, a port town in southwestern Morocco, and one near Al-Askharah, a coastal town in southeastern Oman. They wanted to know how one sand dun can produce multiple notes simultaneously.

No matter where recordings were made near the Moroccan dune, the sands sang consistently at about 105 hertz, in the neighborhood of G-sharp two octaves below middle C. The Omani sands also sang powerfully, but sometimes unleashed a cacophony of almost every possible frequency from 90 to 150 hertz, or about F-sharp to D, a range of nine notes.

Read more about this research in a press release from AGU:
https://news.agu.org/press-release/why-singing-sand-dunes-hum-certain-notes/

Read the original research study here:
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2012GL052540

Video by Derek Sollosi and Sean Treacy.
Images and sounds provided by Simon Dagois-Bohy.