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A conventional, two-dimensional conventional Schroeder diffuser (on the left), compared to a new, "ultra-thin" two-dimensional Schroeder diffuser (at right). Credit: North Carolina State University

A new ultra-thin sound diffuser is 10 times thinner than the diffusers commonly used to reduce echoes and improve the quality of sound in recording studios, concert venues and movie theaters.

Researchers from North Carolina State University and Nanjing University in China developed the new design for the diffuser by reducing the individual cells needed in the diffuser. This reduces both the cost and space needed.

Schroeder diffusers—the most widely used diffuser—is bulky because the size of the diffuser is governed by the wavelength of the sound it needs to diffuse, where the depth of the diffuser is about half of the wavelength of the lowest sound it needs to diffuse.

However, the new, ultra-thin diffuser design requires a thickness of only 5 percent of the sound’s wavelength meaning instead of a two-meter-thick diffuser needed, the new diffuser would only need to be 20 centimeters.

“Diffusers are often made out of wood, so our design would use 10 times less wood than the Schroeder diffuser design,” Yun Jing, an assistant professor of mechanical aerospace engineering at NC State and corresponding author of the study, said in a statement. “That would result in lighter, less expensive diffusers that allow people to make better use of their space.”

The new diffuser consists of evenly spaced squares, much like the Schroeder diffuser.

However, the main difference is the Schroeder diffuser uses squares that are identical in length and width but vary in depth, while the new diffuser uses square that vary in size because each of the squares is an aperture that opens into a thin, underlying chamber.

The chambers all have identical dimensions, while the size of the apertures varies significantly.

“We’ve built fully functional prototypes using a 3D printer and it works,” Jing said. “The design should work just as well using wood.”

Sound waves bounce off the walls in a typical room with flat walls, similar to how light reflects off a mirror. This creates echoes and overlapping sound wave that can reduce the quality of the sound, depending on where a person is in the room.

“Sound diffusers are panels placed on the walls and ceiling of a room to scatter sound waves in many different directions, eliminating echoes and undesirable sound reflections—ultimately improving the quality of the sound,” Jing said.

The study was published in Physical Review X.

      

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