Singing sand

Singing sand


Singing sand dune in Altyn-Emel National Park, Almaty Province, Kazakhstan

Sand blowing off a crest in the Kelso Dunes of the Mojave Desert, California.
Singing sand, whistling sand or barking sand is sand that produces sound. The sound emission may be caused by wind passing over dunes or by walking on the sand.
Certain conditions have to come together to create singingsand:
The sand grains have to be round and between 0.1 and 0.5 mm in diameter
The sand has to contain silica
The sand needs to be at a certain humidity
The most common frequency emitted seems to be close to 450 Hz.
There are various theories about the singing sand mechanism. It has been proposed that the sound frequency is controlled by the shear rate. Others have suggested that the frequency ofvibration is related to the thickness of the dry surface layer of sand. The sound waves bounce back and forth between the surface of the dune and the surface of the moist layer creating a resonance that increases the sound's volume. The noise may be generated by friction between the grains or by the compression of air between them.[1]
Other sounds that can be emitted by sand have been describedas "roaring" or "booming".
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.
Contents [hide]
1 In dunes
2 On the beach
3 See also
4 References
5 Literature6 External links
[edit]In dunes

Singing sand dunes, an example of the phenomenon of singing 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 itemanates 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.
Examples of singing sand dunes include California's Kelso Dunes and Eureka Dunes, sugar sand beaches and Warren Dunes in southwestern Michigan, Sand Mountain in Nevada, the Booming Dunesin the Namib Desert, Africa, Porth Oer (also known as Whistling Sands) near Aberdaron in Wales, Indiana Dunes in Indiana, Barking Sands in Hawaiʻi, Mingsha Shan in Dunhuang, China, and Singing Beach in Manchester-by-the-Sea, Massachusetts. Also near the Al Udeid Air Base west of Doha, in Qatar, and Gebel Naqous, near el-Tor, South Sinai, Egypt.
[edit]On the beach

On some beaches around theworld, dry sand will make a singing, squeaking, whistling, or barking sound if a person scuffs or shuffles their feet with sufficient force.[2][3] The phenomenon is not completely understood scientifically, but it has been found that quartz sand will do this if the grains are very well rounded and highly spherical.[4] It is believed by some that the sand grains must be of similar size, so the sandmust be well sorted by the actions of wind and waves, and that the grains should be close to spherical and have dust-, pollution-, and organic matter-free surfaces. The 'singing' sound is then believed to be produced by shear as each layer of sand grains slides over the layer beneath it. The similarity in size, the uniformity, and the cleanness mean that grains move up and down in unison over thelayer of grains below them. Even small amounts of pollution on the sand grains reduces the friction enough to silence the sand.[3]
Others believe that the sound is produced by the friction of grain against grain that have been coated with dried salt, in a way that is analogous to the way that the resin on the bow produces sounds from a violin string. It has also been speculated that thin layers...