Sound-redirecting prototype could fool eavesdroppers | 6/26/2018 | Staff
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Tuning the instruments that produce some of our most indelible sound waves—guitars, pianos, vocal chords—has become commonplace, expected, easy.

Tuning the surfaces awash in those waves, in real time? A much trickier proposition. But a wave-altering prototype from the University of Nebraska–Lincoln's Mehrdad Negahban and Peking University colleagues could point the way—and find use in applications that range from magnifying signals to disorienting adversaries.

World - Sound - Waves - Triangulate - Evaluate

"We live in a world filled with sound waves that help us communicate, triangulate and evaluate," said Negahban, professor of mechanical and materials engineering. "Our ears let us triangulate the source of sounds. Listening to the reflections of sound waves helps us characterize the properties of the surface that they are reflecting from.

"What if we could change them at will? Could we use this surface to cloak a source or create an illusion?"

Potential - Prototype - Design - Surface - Channels

Though its potential is tantalizing, the prototype's design is relatively straightforward: a surface of 32 vertical channels, each connected to resonators that can be adjusted via horizontal T-shaped sliders.

By extending or retracting the sliders to narrow or widen the corresponding pipes, the team showed that the prototype can dynamically redirect the sound waves passing through the surface.

Idea - Negahban - Thing - Sliders

"It's such a simple idea," Negahban said. "The only thing you have to do is adjust these sliders."

Though the idea of engineering materials or surfaces to strategically refract sound waves is well-established, most existing designs are static, the team said.

Lot - Negahban - Way - Thing

"A lot of what they've done is not tunable," Negahban said. "We looked at that and said, "We can figure out a way to control this thing.""

Computer simulations run by Peking University's Zhong Chen, a doctoral alumnus of Nebraska, allowed the team to predict...
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