Aeolian sound or Aeolian tone is
sound
In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid.
In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...
that is produced by
wind
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hou ...
when it passes over or through objects.
History
Historically,
Aeolus
In Greek mythology, Aeolus or Aiolos (; grc, Αἴολος , ) is a name shared by three mythical characters. These three personages are often difficult to tell apart, and even the ancient mythographers appear to have been perplexed about which A ...
was the Greek ruler of the winds, and the
Ancient Greeks
Ancient Greece ( el, Ἑλλάς, Hellás) was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity ( AD 600), that comprised a loose collection of cultu ...
believed these sounds were the voice of Aeolus.
The earliest known observations about Aeolian sounds from a "scientific" viewpoint were made by
Athanasius Kircher
Athanasius Kircher (2 May 1602 – 27 November 1680) was a German Jesuit scholar and polymath
A polymath ( el, πολυμαθής, , "having learned much"; la, homo universalis, "universal human") is an individual whose knowledge spans ...
in 1650.
[
]
Physical cause
An Aeolian tone is produced when air passes over an obstacle, resulting in trailing vortices with oscillatory behavior. These eddies can have strong periodic components, resulting in a steady tone.[ This phenomenon is the main topic of ]aeroacoustics Aeroacoustics is a branch of acoustics that studies noise generation via either turbulent fluid motion or aerodynamic forces interacting with surfaces. Noise generation can also be associated with periodically varying flows. A notable example of th ...
;
For air moving over a cylinder, empirical data shows that an Aeolian tone will be produced with the frequency
: ,
where is the air velocity, is the diameter of the cylinder, and is the Strouhal number
In dimensional analysis, the Strouhal number (St, or sometimes Sr to avoid the conflict with the Stanton number) is a dimensionless number describing oscillating flow mechanisms. The parameter is named after Vincenc Strouhal, a Czech physicist who ...
, which has a value of about 0.2.[
]
Notable occurrences
Aeolian sounds can be produced in the rigging of a sail-powered ship. The vortex trails produced as the wind passes over a rope produce a sound with a frequency that varies with the velocity of the wind and the thickness of the rope. Each doubling of the wind velocity results in an octave increase in the tone, allowing up to a six octave variation in a strong, gusty wind. Ships may also carry Helmholtz resonator
Helmholtz resonance or wind throb is the phenomenon of air resonance in a cavity, such as when one blows across the top of an empty bottle. The name comes from a device created in the 1850s by Hermann von Helmholtz, the ''Helmholtz resonator'', wh ...
s that amplify these sounds. Aeolian sounds can also be heard among the openings in limestone cliffs.
Some songs have been written to emulate these varying wind sounds, such as " The Winter Wind" by Frédéric Chopin
Frédéric François Chopin (born Fryderyk Franciszek Chopin; 1 March 181017 October 1849) was a Polish composer and virtuoso pianist of the Romantic period, who wrote primarily for solo piano. He has maintained worldwide renown as a leadin ...
or "Tempest
Tempest is a synonym for a storm.
'' The Tempest'' is a play by William Shakespeare.
Tempest or The Tempest may also refer to:
Arts and entertainment Films
* ''The Tempest'' (1908 film), a British silent film
* ''The Tempest'' (1911 film), a ...
" by Ludwig van Beethoven
Ludwig van Beethoven (baptised 17 December 177026 March 1827) was a German composer and pianist. Beethoven remains one of the most admired composers in the history of Western music; his works rank amongst the most performed of the classical ...
.[
Aeolean sound was heard around ]San Francisco, California
San Francisco (; Spanish for " Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the fourth most populous in California and 17th ...
beginning June 5, 2020, as a consequence of high winds and new walkway slats installed on the Golden Gate Bridge
The Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the strait connecting San Francisco Bay and the Pacific Ocean. The structure links the U.S. city of San Francisco, California—the northern tip of the San Francisco Pen ...
.
See also
*Aeolian harp
An Aeolian harp (also wind harp) is a musical instrument that is played by the wind. Named for Aeolus, the ancient Greek god of the wind, the traditional Aeolian harp is essentially a wooden box including a sounding board, with strings stretched ...
References
[{{cite book , first=Joyce J. , last=Bartell , year=1982 , author2=Annenberg School of Communications (University of Southern California). Center for Study of the American Experience , title=The Yankee mariner & sea power: America's challenge of ocean space : papers from a conference , publisher=Transaction Publishers , isbn=0-88474-105-2 , page=270 , url=https://books.google.com/books?id=0tLHbR65GqwC&pg=PA270 ]
Wind power
Sound