Re: Singing to the tune of sand & Booming Sands

On Thu, 13 Jul 2006 14:30:42 +0000, Sam Wormley wrote:

Singing to the tune of sand
http://physicsweb.org/articles/news/10/7/5/1

12 July 2006

Ever since Marco Polo, explorers have told stories about strange sounds
they have heard in the desert. It is known that these sounds are
produced by sand dunes when they avalanche, but the exact mechanism
behind the phenomenon has remained a mystery. Now, Stéphane Douady
from the French national research council and colleagues have proposed
that the sounds come from the synchronisation of the motion of the sand
grains as they pass over each other -- and not from the grains
producing excitations on the surface of the dune, as was previously
believed (Phys. Rev. Lett. 97 018002).

Singing dunes are one of the most puzzling and impressive natural
phenomena. The sounds produced can be heard up to 10 kilometres away
and resemble a drum, a low-flying jet or even an organ.. The sounds can
be as loud as 105 decibels and have frequencies between about 65 and
110 Hertz depending on where the sand comes from. Using sand shipped
from the Ghord Lahmar region in Morocco to their lab, Douady and
colleagues found they could produce notes from the sand simply by
pushing the sand grains together by hand or using a metal blade (figure
1). This means that the sounds are nothing to do with the dune itself
but are produced by the motions of the sand grains -- not from the
entire dune resonating.

See: http://physicsweb.org/articles/news/10/7/5/1



Also: Booming Sands (Jan 2005)
http://www.pbs.org/wgbh/nova/programs/int_eart.html
http://www.pbs.org/wgbh/nova/sciencenow/3204/04.html

See also _Dune_, which among many other things postulated drumsand. I'll
admit to wondering how much time Frank Hebert spent in the desert. :-)

Interesting stuff.

--
#191, ewill3@xxxxxxxxxxxxx
It's still legal to go .sigless.

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