t h e s i n g i n g d u n e s

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Tuesday, 12 February 2013

19:13:54

Singing or booming dunes

were first documented over 1,200 years ago in the ancient Chinese Tun Huang Lu manuscript.

During the centuries they have aroused the curiosity of explorers scientists and emperors from Marco Polo Afghan Emperor barber to Charles Darwin.

When Marco Polo heard it in China, he suspected evil spirits. When residents of Copiapo, Chile, heard it emanating from a sandy hill, they dubbed the peak El Bramador, for its roars and bellows.

Scientists today call it "singing sand," but they're all referring to the same thing: As sand grains shuffle down the slopes of certain sand dunes, they produce a deep, groaning hum that reverberates for miles.

But how these dunes produce this "music" remains a much debated mystery. Another vexing question is why different dunes sing different tunes—and how can some even sing more than one note at a time?

The song of the dunes

 

 dunesomega123

 

Uploaded on 27 Oct 2008

 

The song of the dunes introduced by Stéphane Douady. Since Marco Polo this strange sounds that can be heard in some deserts fanscinates. Here Stéphane Douady shows the different sounds that can be made, as soon as this singing sand it is sheared, with the hand, the feet, or in avalanches. Recorded on a singing dune in Morocco. A movie from Etienne Chaillou and Mathias Thery.

A trio of Parisian biophysicists think they know the answer. It's not necessarily the motion of the sandy ocean that determines the pitch of the note—it's the size of the grains, though why the size matters is still unknown.

 

The researchers first tracked down a pair of singing dunes, one in Morocco, the other in Oman. Working literally by the seat of their pants, they scooted feet-first down the hills to trigger the avalanches. They found that, while the Moroccan hill moaned at a steady 105 Hz—or a low G sharp—the Omani dunes sang a nine-note blare that ranged from 90 to 150 Hz.

 

 

Sources: http://news.nationalgeographic.com/news/2012/10/121031-singing-sand-dunes-physics-science-whistling/

Shannon Fischer for National Geographic News Published October 31, 2012 Listen to Sand Dunes Sing