Singing sand
Encyclopedia
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
that produces sound. The sound emission may be caused by wind passing over dune
Dune
In physical geography, a dune is a hill of sand built by wind. Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind...
s or by walking on the sand.
Certain conditions have to come together to create singing sand:
- The sand grains have to be round and between 0.1 and 0.5 mm in diameterDiameterIn geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...
. - The sand has to contain silica.
- The sand needs to be at a certain humidityHumidityHumidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...
.
The most common frequency emitted seems to be close to 450 Hz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
.
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 of vibration 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.
Other sounds that can be emitted by sand have been described as "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.
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 decibelDecibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
s, lasting as long as several minutes, that occurs in about 35 desert
Desert
A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...
locations around the world. The sound is similar to a loud, low-pitch, rumble, and it emanates from the crescent-shaped dunes, or barchan
Barchan
A barchan dune, also barkhan is an arc-shaped sand ridge, comprising well-sorted sand. This type of dune possesses two "horns" that face downwind, with the slip face at the angle of repose of sand, or approximately 35 degrees . The upwind side is packed by the wind, and stands at about 15 degrees...
s. The sound emission accompanies a slumping or avalanching movement of the sand, usually triggered by wind passing over the dune
Dune
In physical geography, a dune is a hill of sand built by wind. Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind...
or by someone walking near the crest.
Examples of singing sand dunes include California's Kelso Dunes
Kelso Dunes
Kelso Dunes, also known as the Kelso Dune Field, is the largest field of eolian sand deposits in the Mojave Desert. The region is protected by the Mojave National Preserve and is located near the town of Baker, San Bernardino County, California and the Preserve Visitor Center...
and Eureka Dunes
Eureka Valley Sand Dunes
The Eureka Valley Sand Dunes are located in the southern part of Eureka Valley, in northern Inyo County in eastern California, in the southwestern United States...
; sugar sand
Sugar sand
Sugar sand, found in some areas of the Eastern United States, is a fine silt made up of ultrafine mineral sand mixed with a large percentage of organic granules. Because of its lightness it can easily form quicksand in hollows. In New Jersey, quicksand is often referred to as "sugar sand." Even...
beaches and Warren Dunes in southwestern Michigan
Michigan
Michigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....
; Sand Mountain
Sand Mountain (Nevada)
Sand Mountain is a Singing sand dune east of Fallon, Nevada along U.S. Route 50. The dune is two miles long and high.It lies on the edge of the ancient Lake Lahontan, that for the most part dried up 9,000 years ago. Sand Mountain Recreation Area is managed by the Bureau of Land Management and is...
in Nevada
Nevada
Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...
; the Booming Dunes in the Namib Desert
Namib Desert
The Namib Desert is a desert in Namibia and southwest Angola that forms part of the Namib-Naukluft National Park, the largest game reserve in Africa. The name "Namib" is of Nama origin and means "vast place"...
, Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
; Porth Oer (also known as Whistling Sands) near Aberdaron
Aberdaron
Aberdaron is a community and former fishing village at the western tip of the Llŷn Peninsula in the Welsh county of Gwynedd. It lies west of Pwllheli and south west of Caernarfon, and has a population of 1,019. It is sometimes referred to as the "Land's End of Wales"...
in Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
; Indiana Dunes in Indiana
Indiana
Indiana is a US state, admitted to the United States as the 19th on December 11, 1816. It is located in the Midwestern United States and Great Lakes Region. With 6,483,802 residents, the state is ranked 15th in population and 16th in population density. Indiana is ranked 38th in land area and is...
; Barking Sands
Barking Sands
Barking Sands is a beach on the island of Kauaʻi in the US state of Hawaiʻi. It is the location of Pacific Missile Range Facility, a rocket launch site and also an official Missile Defense Testing Area, both controlled by the United States Navy....
in Hawaiʻi; Mingsha Shan in Dunhuang
Dunhuang
Dunhuang is a city in northwestern Gansu province, Western China. It was a major stop on the ancient Silk Road. It was also known at times as Shāzhōu , or 'City of Sands', a name still used today...
, China; Singing Beach in Manchester-by-the-Sea, Massachusetts
Manchester-by-the-Sea, Massachusetts
Manchester-by-the-Sea is a town on Cape Ann, in Essex County, Massachusetts, in the United States. As of the 2000 census, the town population was 5,228.-History:...
; near the Al Udeid Air Base
Al Udeid Air Base
Al Udeid Air Base is a military base west of Doha, Qatar. It houses foreign coalition personnel and assets. It is host to a forward headquarters of United States Central Command, headquarters of United States Air Forces Central Command, and home to both No. 83 Expeditionary Air Group RAF and the...
west of Doha
Doha
Doha is the capital city of the state of Qatar. Located on the Persian Gulf, it had a population of 998,651 in 2008, and is also one of the municipalities of Qatar...
, in Qatar
Qatar
Qatar , also known as the State of Qatar or locally Dawlat Qaṭar, is a sovereign Arab state, located in the Middle East, occupying the small Qatar Peninsula on the northeasterly coast of the much larger Arabian Peninsula. Its sole land border is with Saudi Arabia to the south, with the rest of its...
; and Gebel Naqous, near el-Tor
El-Tor
El-Tor , also transliterated as Al-Tur and At-Tur and known as Tur Sinai, formerly Raithu, is the capital of South Sinai Governorate of Egypt, located at the Sinai Peninsula...
, South Sinai, Egypt.
On the beach
On some beaches around the world, dry sand will make a singing, squeaking, whistling, or barking sound if a person scuffs or shuffles their feet with sufficient force. 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. It is believed by some that the sand grains must be of similar size, so the sand must 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 shearShear stress
A shear stress, denoted \tau\, , is defined as the component of stress coplanar with a material cross section. Shear stress arises from the force vector component parallel to the cross section...
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 the layer of grains below them. Even small amounts of pollution on the sand grains reduces the friction enough to silence the sand.
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
Bow (music)
In music, a bow is moved across some part of a musical instrument, causing vibration which the instrument emits as sound. The vast majority of bows are used with string instruments, although some bows are used with musical saws and other bowed idiophones....
produces sounds from a violin string. It has also been speculated that thin layers of gas trapped and released between the grains act as "percussive cushions" capable of vibration, and so produce the tones heard.
Not all sands sing, whistle or bark alike. The sounds heard have a wide frequency range that can be different for each patch of sand. Fine sands, where individual grains are barely visible to the naked eye, produce only a poor, weak sounding bark. Medium-sized grains can emit a range of sounds, from a faint squeak or a high-pitched sound, to the best and loudest barks when scuffed enthusiastically.
Water also influences the effect. Wet sands are usually silent because the grains stick together instead of sliding past each other, but small amounts of water can actually raise the pitch of the sounds produced. The most common part of the beach on which to hear singing sand is the dry upper beach above the normal high tide line, but singing has been reported on the lower beach near the low tide line as well.
Singing sand has been reported on thirty-three beaches in the British Isles including in the North of Wales, on the little island of Eigg in the Scottish Hebrides and at a number of beaches along the Atlantic Coast; at Souris, on the eastern tip of Prince Edward Island, in Manchester-by-the-Sea, Massachusetts,, as well as in the fresh water of Lake Superior and in other places.
See also
- Bouncing stonesBouncing stonesThe Bouncing Stones Site or beach is in the Daintree National Park in the far north of Queensland, Australia. The site is sacred to the Kuku Yalanji Aboriginals of the area and was an area where the women of the tribe discussed their secret women's business. The site takes its name because stones...
- Bruce Peninsula National ParkBruce Peninsula National ParkBruce Peninsula National Park is a national park on the Bruce Peninsula in Ontario, Canada. Located on a part of the Niagara Escarpment, the park comprises 156 square kilometres and is one of the largest protected areas in southern Ontario, forming the core of UNESCO's Niagara Escarpment World...
- Colossi of MemnonColossi of MemnonThe Colossi of Memnon are two massive stone statues of Pharaoh Amenhotep III. For the past 3400 years they have stood in the Theban necropolis, across the River Nile from the modern city of Luxor.-Description:The twin statues depict Amenhotep III The Colossi of Memnon (known to locals as...
- Kelso DunesKelso DunesKelso Dunes, also known as the Kelso Dune Field, is the largest field of eolian sand deposits in the Mojave Desert. The region is protected by the Mojave National Preserve and is located near the town of Baker, San Bernardino County, California and the Preserve Visitor Center...
- Indiana Dunes
- MistpouffersMistpouffersMistpouffers are unexplained reports that sound like a cannon or a sonic boom. They have been heard in many waterfront communities around the world such as the banks of the river Ganges in India, the East Coast and inland Finger Lakes of the United States, as well as areas of the North Sea, Japan...
- The HumThe HumThe Hum is a generic name for a series of phenomena involving a persistent and invasive low-frequency humming noise not audible to all people. Hums have been reported in various geographical locations. In some cases a source has been located. A Hum on the Big Island of Hawaii, typically related...
Literature
- F. Nori, P. Sholtz, and M. Bretz "Booming Sands". Scientific American 277(3), 84 (September 1997).
- P. Sholtz, M. Bretz, and F. Nori "Sound-producing sand avalanches". Contemporary Physics 38(5), 329-342 (October 1997).
- K. Ridgeway and J. B. Scotton "Whistling sand beaches in the British Isles". Sedimentology 20 (2), 263–279 (1973).
- B. Andreotti "The Song of Dunes as a Wave-Particle Mode Locking". Phys. Rev. Lett. 93, 238001 (2004).
- S. Douady et al. "Song of the Dunes as a Self-Synchronized Instrument". Phys. Rev. Lett. 97, 018002 (2006).
- L. Bonneau, B. Andreotti and E. Clément "Surface elastic waves in granular media under gravity and their relation to booming avalanches". Phys. Rev. E 75, 016602 (2006).
- N.M. Vriend, L. Hunt, R.W. Clayton, C.E. Brennen, K.S. Brantley, and A. Ruiz-Angulo "Solving the mystery of booming sand dunes". Geophysical Research LettersGeophysical Research LettersGeophysical Research Letters is a semi-monthly peer reviewed scientific journal published by the American Geophysical Union that was established in 1974...
34, 2007GL030276 (2007). - B. Andreotti, L. Bonneau and E. Clément "Comment on 'Solving the mystery of booming sand dunes'". Geophys. Res. Lett. 35, L08306 (2008).
External links
- The Bibliography of Aeolian Research
- Enigma of the Singing Dunes article on physics.org
- Location information for booming sand dunes around the World
- Singing Sand Dunes in Kazakhstan, also called Singing Barkhan
- Explanation, Video and Audio clips
- Video clips of Singing Sand Dunes
- Singing and Booming Sand Dunes of California and Nevada