PASADENA, Calif.--Marco Polo heard the sounds and wrote of evil spirits that could fill the desert air with the emanations of musical instruments, of drums, and the clash of arms. Today's desert explorers still wonder at the booming sands: loud, low-pitched droning that accompanies the avalanching of sand down the leeward face of a large dune, and may continue to rumble for up to a minute after the avalanche stops.

Researchers at the California Institute of Technology wondered, too, and now believe the internal structures of booming dunes tend to sustain and amplify certain notes, acting like the body of a well-crafted musical instrument. These structures have been computer simulated, and the new model's behavior is consistent with years of field observations using seismic refraction, frequency measurements, and subsurface soil sampling.

Melany L. Hunt, professor and executive officer of mechanical engineering at Caltech, will describe this new understanding of an ancient desert song on Wednesday, January 17, in "Booming Sand Dunes," the fourth and final program of the Fall/Winter 2006-07 Earnest C. Watson Lecture Series.

Hunt compares the music of these booming dunes with the sound of a cello. "In a cello, the musician bows the strings, and the sound is amplified through vibrations of the cello and the enclosed air. In the dune, we excite the system by avalanching the sand on the upper surface, and sound is amplified in an dry, loose upper layer of sand."

Hunt will present the lecture at 8 p.m. on January 17 in Beckman Auditorium, 332 South Michigan Avenue, south of Del Mar Boulevard, on the Caltech campus in Pasadena. Seating is available on a free, no-ticket-required, first-come, first-served basis.

Caltech has offered the Watson Lecture Series since 1922, when it was conceived by the late Caltech physicist Earnest Watson as a way to explain science to the local community.

For more information, call (626) 395-4652. Outside the greater Pasadena area, call toll-free, 1(888) 2CALTECH (1-888-222-5832).

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Contact: Kathy Svitil (626) 395-8022 ksvitil@caltech.edu

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