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Booming Sands
Mon Oct 11, 2004
Listen in RealAudio 
The crashing and booming of waves upon a sandy beach are all part of the shoreline
experience. But ocean waves are not the only natural force to play music on the sand.
Hi, I’m Bryan Yeaton for The Weather Notebook.
Let’s head inland to desert sands. On the dunes, sand becomes the instrument and
wind, the key player. There, sand hills have been heard to whistle, sing and
boom.
Witnesses have compared these sounds to a ship's horn, the tolling of underground
bells, the beat of drums, or the twanging of a monster harp. The notes of booming
desert sands sound much lower than the whistling notes of dune or beach sand. The
higher pitched sounds are more fleeting, usually lasting for less than a
second.
Scientists studying the phenomenon generally agree that the sounds derive from sand
in motion, caused by the rubbing of grains against each other. Sounds begin when
wind blows sand from dune crests and can continue to resound when winds die if the
sand grains continue to avalanche downslope.
The sound frequency depends on grain size, and the grain surface texture controls the
amplitude. Sand dryness is also important. Whistling occurs where quartz sand is
rounded and highly spherical.
The sounds of the grains rubbing together during motion are then further amplified by
the stationary sand beneath, which acts as a giant sounding board or organic amplifier
to produce the great volume.
Descriptions of booming dunes have graced Middle East literature for at least 1,500
years and Chinese literature for 1,200 years. Sand Mountain southeast of Fallon,
Nevada is an excellent place to hear booming sands here in the United
States.
Thanks to our contributing writer, meteorologist Keith Heidorn. The Weather Notebook
is a program of the Mount Washington Observatory, funded by Subaru of America.
Today's Links
What are \"booming sands\" and what causes the sounds they make?
http://www.sciam.com/askexpert_question.cfm?articleID=000AD4E4-6158-1C71-9EB7
809EC588F2D7
Booming Sands:
http://www.aip.org/radio/scripts/booming_sands.txt
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