Sand dunes "hum" in some areas of the planet, and their "melodies" – always a low sound, similar to a buzzing – have aroused human curiosity for centuries. Marco Polo spoke of them, and also Charles Darwin in his Voyage of the Beagle . The sound is a soft hum at a frequency equivalent to the lower half of the musical range of a cello . This sound is only heard when the sand slides down its slopes. And when the wind causes avalanches, a kind of "chorus" is heard.
In a new scientific study to explain the phenomenon, a team of physicists from the Diderot University in Paris (France) have shown for the first time that the same dune can emit different musical notes . Using recordings taken in Morocco and Oman, they identified a specific note range unique to each dune. For example, in the sands of Oman a range of nine notes was detected, from Fa to Re, as announced by the researchers in the journal Geophysical Research Letters. The scientists also found that the size of the sand grains could influence the intensity of sound and pitch. And that the more the size of the sand grains varies in the same dune, the greater the range of notes that is produced .
