Singing Sand Dunes

From Wikipedia, the free encyclopedia

It has been suggested that this article or section be merged into singing sand. (Discuss)

Singing sand dunes, an example of the phenomenon of "musical sand", produce a sound described as roaring, booming, squeaking, or the Song of Dunes. This is a natural sound phenomenon of up to 105 decibels lasting as long as several minutes that occurs in about 35 desert locations around the world. The sound is similar to a loud, low-pitch, rumble, and it emanates from the crescent-shaped dunes, or barchans. The sound emission accompanies a slumping or avalanching movement of the sand, usually triggered by wind passing over the dune or by someone walking near the crest. Scientists announced in 2004 that they had discovered how the singing sand phenomenon works: collisions between grains of sand emit surface elastic waves that in turn, cause the motions of the grains to become synchronized. The sound in the air is emitted by the vibration of the sand surface (by the surface elastic waves) that behaves like a loudspeaker. The resonance of the outer layer of the dune controls the threshold of the phenomenon: a sufficiently deep layer of dry sand at the surface is necessary for booming to occur. The scientists suggested that the most beautiful sounds come from dunes in Oman.

The particular note produced by the dune, between 60 and 105 Hertz, is controlled by the rate of collision in the shear band separating the avalanche from the static part of the dune. For spontaneous avalanches, the frequency is controlled by gravity and by the size of the sand grains.