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02 October 2002

Listen up: E-textiles for sound detection

A prototype "e-textile," a special cloth interwoven with microelectronic components, may soon allow a person to pinpoint sources of faint sounds, engineers say.

Under a cooperative venture, called the Stretch program, between the University of Southern California and Virginia Tech, engineers said this new cloth functions as a supersensitive detection array.

Stretch is the first time an e-textile can perform all aspects of such a complicated process, the engineers said.

"Modern methods of making fabrics allow extraordinary control over materials and properties," said Robert Parker, director of the Arlington, Va., campus of the USC School of Engineering's Information Sciences Institute and coprincipal investigator on Stretch. "And cloth has properties that can be very useful for certain electronic applications. We can easily and cheaply make very large pieces of cloth light and very strong that can be stretched over frames into any desired shape."

The material Parker and his coinvestigator, Mark Jones of the Configurable Computing Laboratory at Virginia Polytechnic Institute and State University in Blacksburg, Va., created could deploy in various ways: as a parachute, a tent, a camouflage net, a sail, or simply a bolt of cloth rolled compactly away until needed.

Modern methods of detection use arrays of individual detectors, arranged in a pattern, and combine the reports from all into a detailed image using computational algorithms.

Parker has worked on arrays made up of small, stand-alone detectors that individually go in the environment and communicate with one another by radio.

But embedding similar units into fabric has advantages, Parker said. "The signals they exchange can be carried on wires in the fabric. This greatly lowers the power requirements to operate the system."

Additionally, an adversary can pick up radio signal exchanges, which could give away not only the fact that surveillance is under way but also its position.

"Forming it into a fabric makes it electronically silent," said Jones. Additionally, while embedding the detectors in fabric sacrifices the flexibility of individual stand-alone units, it ensures the units will be automatically be in the right positions relative to one another to do their jobs optimally.

The Stretch fabric will begin testing in field environments in November. The engineers still have to solve some problems. "While fabric manufacturing technology is advanced, we expect that the large number of components and the inherent imprecision in the process will make it difficult to weave very large, fault-free arrays," Parker said.

Making these tough enough to stand up to weather and rough handling in field conditions is another challenge.

However, in preliminary tests, the material proved robust. It can be rolled (though not folded) and unrolled without damage. And even when numbers of the individual units fail, the detector still functions effectively.

Will soldiers' wardrobes someday include sound detector sweaters, satellite signal antenna hats, or chemical sniffer vests? Not right away, but perhaps someday.