Singing sand, whistling sand or barking sand is sand that produces sounds of either high or low frequency under pressure. The sound emission is usually triggered by wind passing over dunes or by walking on the sand. The sound is generated by shear stress.
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 diameter
- The sand has to contain silica
- The sand needs to be a certain humidity
The most common frequency emitted seems to be close to 450 Hz.
Importantly, there are still scientific controversies on the details of the singing sand mechanism (see references). 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.
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.
Singing sand 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 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.
Examples of singing sand dunes include California's Kelso Dunes
and Eureka Dunes
, sugar sand
beaches and Warren Dunes
in southwestern Michigan
, Sand Mountain
, the Booming Dunes in the Namib Desert
, Porth Oer (also known as Whistling Sands) near Aberdaron
, Indiana Dunes
, Barking Sands
in Hawaii, and Singing Beach in Manchester-by-the-Sea, Massachusetts
- Nori, Franco; Sholtz, Paul; & Bretz, Michael (September 1997). "Booming Sands", Scientific American, 277(3), 84.
- Sholtz, Paul; Bretz, Michael; & Nori, Franco (October 1997). "Sound-producing sand avalanches", Contemporary Physics, 38(5), 329-342.
- K. RIDGWAY, J. B. SCOTTON (1973) Whistling sand beaches in the British Isles Sedimentology 20 (2), 263–279
- 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, A. Ruiz-Angulo " Solving the mystery of booming sand dunes [[Geophysical Research Letters] 34, 2007GL030276 (2007)
- B. Andreotti, L. Bonneau and E. Clément " Comment on 'Solving the mystery of booming sand dunes'" Cond-mat 0710.1815 (2007).
- Explanation, Video and Audio clips
- Video clips of Singing Sand Dunes
- Singing and Booming Sand Dunes of California and Nevada