This is scientific American's 60 second science.

I'm Christopher Intagliata.

Got a minute?

Oh!

T.

The sound of supernatural spirits talking? Well, no, but that's what it sounded like to Marco Polo as he traveled through China's Lop Desert in the 13th century.

He also described the sound as a variety of musical instruments.

And in reality, the mysterious noises are the product of what could be considered to be an unusual sort of instrument. The desert... the

product of what could be considered to be an unusual sort of instrument, the desert sand dunes.

And it's a sound that again it's very similar to kind of the tones you get on its

shallow.

Melanie Hunt, a mechanical engineer at Caltech.

The dunes sing when sand avalanches down the side.

Which would then be somewhat equivalent to using the bow on the strings of the cello.

Hunt's and her colleagues recorded the sounds produced close at home by California's

Kelso and Eureka Dunes.

They used four dozen geophones, microphones stick in the sand, and they mapped the dunes structure with ground-penetrating

radar.

Turns out dunes that sing are built differently from silent dunes.

They're topped with an even layer of dry sand about five feet thick on top of all the damp sand below

And that layer of dry sand is like the body of an instrument. It traps and amplifies certain frequencies more than others And so really the size of the instrument and of the same thing with this dune. When the sand avalanches, it shoots off sound waves of various frequencies.

Those waves then travel through the dry sand, hit the wet layer, bounce back, hit the air on

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