Engineers Develop Acoustic Metamaterial That Can Cancel 94 Percent Of Sound


Blocking sounds and creating silence even within a noisy environment is possible with the help of acoustic metamaterials.

Researchers at Boston University discovered that they can harness their mathematical skills and use 3D printing to produce a design that can essentially mute noise without limiting air passage.

Quiet Amid The Noise

Reza Ghaffarivardavagh, a graduate student and research assistant in the Department of Mechanical Engineering at BU, said they wanted to create something that can help resolve today's problems. He said living in a busy city like Boston makes it quite difficult to find quiet moments.

Ghaffarivardavagh and Xin Zhang, a professor at the College of Engineering and Photonics Center, created a sound barrier that blocks noise up to 94 percent. Details of their study, including the specific mathematical measurements, are published in the journal Physical Review B.

"This ultra-open metamaterial design, leveraging a Fano-like interference, enables high-performance sound silencing in a design featuring a large degree of open area, which may find utility in applications in which highly efficient, air-permeable sound silencers are required, such as smart sound barriers, fan or engine noise reduction, among other," wrote the authors.

Ghaffarivardavagh and Zhang both share a passion for metamaterials and found a way to acoustic metamaterials to current structural designs. Though relatively young, Zhang believes acoustic metamaterial is the future in the field.

Effective Noise Reduction

The pair hypothesized that by shaping metamaterials in a way that will prevent sound, not air, from reverberating in an open space, they can greatly reduce noise levels.

The researchers modeled a plastic structure created through 3D printing. They attached the end of the pipe into a loudspeaker. The other end was sealed with the sound barrier they created using their mathematical and physical dimensions.

The metamaterial acted like a mute button ringing inside the pipe. What remained of the speaker is a screeching sound that echoed inside the lab.

"We can design the outer shape as a cube or hexagon, anything really," Zhang said. "When we want to create a wall, we will go to a hexagonal shape" that can fit together like an open-air honeycomb structure."

Zhang added that the design can be used to a variety of real-world applications such as reducing the vibrations of an MRI machine.

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