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Tracking the sounds buried in sand dunes.

In the dark hours of early morning, before the scorching heat arrives, Melany Hunt, professor of mechanical engineering at the California Institute of Technology, Pasadena, and her research team climb massive sand dunes in the Mojave Desert's Death Valley.

With heavy equipment in tow, they listen for sounds beneath the billions of granules--an acoustic stirring that has been noted for centuries. The team investigated the characteristics of waves emitted during what are known as burping and booming emissions. Their findings are detailed in Physics of Fluids.

Booming sand dunes produce a persistent, low-frequency sound that resembles a pure note from a musical instrument. Prior to the onset of booming, the emission consists of short bursts or burps of sound of smaller amplitudes. The researchers discovered that the surface and volumetric signals are present, but with distinct features and properties.

To their surprise, Hunt and her colleagues also learned that, by providing an impulse on the surface of the massive mound of sand--a simple hammer blow on a plate, for example--they could trigger the natural resonance within the dune. "We had never before observed this in the literature," reveals Hunt.

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Title Annotation:Death Valley
Publication:USA Today (Magazine)
Article Type:Brief article
Geographic Code:1U9CA
Date:Jun 1, 2016
Words:189
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