Scientists have developed a superior sound-reflecting material. The "retroreflector" technology can bounce back sound waves in the direction they came from.

Previous retroreflectors relied on a combination of angled reflections to return sound waves to their source direction, but the latest material offers a direct reflection. The new technology allows the material to perform at a wider effective range, reflecting sound waves across a range of 70 degrees in either direction.

"The technology makes use of two engineered materials," Yun Jing, an associate professor of mechanical and aerospace engineering at North Carolina State University, said in a news release. "The first layer focuses the incoming sound waves onto a second layer, which then sends the sound waves back to their source. We were inspired by a similar approach used in optics research, but we think we are the first to use this technique in the acoustics field."

Previous retroreflector technologies used an array of rectangular pits, which directed sound waves to the bottom of the pits before redirecting them back to where they came from.

"Designs using that approach can be bulky, and have a fairly narrow range of angles that they can reflect properly," Jing said. "Our technology is both slimmer and effective across a wider range of angles."

The new retroreflector composite material is both effective and efficient. When sound waves hit the technology at perpendicular angle, 60 percent of the sonic waves are returned. When sound waves strike at a 70 degree angle, 40 percent of the waves are reflected.

Scientists described their technology this week in the journal Physical Review Letters.

"We have a fully functional prototype now, and our next steps include fine-tuning the technology for use in specific applications, such as medical ultrasound," Jing said. "Frankly, we think there are likely applications that we haven't thought of yet."

Acoustic retroreflectors could prove useful for a variety of technologies -- including music and communications-related technologies -- that rely on sound waves to function properly.

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