Monday, April 07, 2003

Stéphane Douady:

A piece about singing sand in this week's Science caught my eye. Mathematician Douady's team built a 2-meter annulus to contain 72-kg of Moroccan sand, which they churned in order to get it to hum. Sort of like running a moistened finger around a wine-glass, but on a grand, government-funded, scale. (As a government program officer, I'd love to see the justification the scientists and the French grants officers used to fund the study at the Ecole Normale Supérieur in Paris...)

I remember hearing about dunes that made noise when I was a child, and to see this topic again brought back some memories of old encyclopedias. Sure enough, the web provides a way to hear singing sand too -- there are people who dedicate their lives to these things.

If you have walked over snow, you are familiar with squeaking sounds that solids can make under pressure and shear. Some beach sands make these squeaking sounds when you walk on them as well.

Prof. Shigeo Miwa of Kyoto has a fascination for sand, and provides a recording of a squeaking beach sand from two Japanese beaches, Kotohiki and Kagunari. The website does not explain how the sounds were obtained, but I suspect they were from shaking these beach sands in a container designed to amplify the sounds. Amazing. Think of the time devoted to this...

Much more impressive are the sounds made by the booming dune in the Badain-jaram desert, Mongolia. Franco Nori, at the University of Michigan, also has a good recording of the booming dune Sand Mountain, in Nevada.

Both of these made my hair stand on end, and I'm sure the real thing is even creepier. Sort of like having a Tibetan horn blown in your ear. For anybody who has heard a glacier groan, this is another take on how frightening a completely natural phenomenon can be to the human psyche. Unfortunately, Prof. Miwa points out that most singing sand is extremely sensitive to humidity and pollution (the requirement being for rounded, very dry, pure quartz sand), and many sites previously known to sing are now silent. We will have to rely on recordings for many of these (fortunately, as the note on Franco Nori's page indicates, the people recording the Sand Mountain piece were real pros -- Bernie Krause, David Criswell, Jim Metzner with some by Michael Bretz as well).

In the U.S., the following places are known to have booming sand:
  • Sand Mountain, Fallon, Nevada
  • Crescent Dune, Tonopah, Nevada
  • Kelso Dune, Mojave, California

Some reports of booming dunes also have come from the Eureka and Panamint dunes areas in California, and from Big Dune, Nevada.