Another Stab at Stealth

It seems like once a week we receive a report of a new stealth technology. This time, we are dealing with sound instead of light. According to the MIT Technology Review scientists has used the first acoustic metamaterial ever produced to focus ultrasound waves. Metamaterials are used to bend light in ways that appear to violate the laws of physics, creating so-called superlenses, for ultra-high-resolution optical imaging, as well as invisibility cloaks. They have a negative index of refraction allowing them to bend light backward. now it seems they can do the same thing with sound waves. Going beyond theory, Nicholas fang, an assistant professor of mechanical science and engineering at the University of Illinois at Urbana-Champaign, has demonstrated significant refraction of light. While his team still hasn’t exceeded the diffraction limit, their device, an aluminum array of narrow-necked cavities whose dimensions are tuned to interact with ultrasound waves, when filled with water, resonates the sound waves hitting it.

Acoustic Super Lens\
When filled with water, the holes in this aluminum plate act as resonant cavities that can focus ultrasound waves.

Photo: Nicholas Fang


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