Credit: Photo by Cydney Scott for Boston University
The mathematically designed, 3D-printed acoustic metamaterial is shaped in such a way that it sends incoming sounds back to where they came from, Ghaffarivardavagh and Zhang say. Inside the outer ring, a helical pattern interferes with sounds, blocking them from transmitting through the open center while preserving air’s ability to flow through.

By combining math with 3D printing, researchers from Boston University have created a new material that seemingly defies logic: Light and air have no trouble passing through it — but sound cannot.

When it comes to blocking out sound, traditional methods have involved acoustic paneling that absorbs the sound, like soundproof recording booths, a concert hall or even earplugs.

A new paper published in the journal Physical Review B might change all that, however, the researchers describe the work that went into creating what they call their “acoustic metamaterial.”

Moving air creates noise, there’s just no way around it. That’s how sound works here on Earth, and why you can’t hear anything in the vacuum of space.

The researchers Reza Ghaffarivardavagh and Xin Zhang from Boston University have come up with a very efficient sound blocking solution that works without impeding the actual movement of air.

 

 

The Boston University researchers developed a new material engineered with a 3D structure that can reflect the vibrations and disturbances in the air that create noise, back towards their source. The sounds don’t magically disappear, but through a strategic installation and positioning of this new metamaterial, the sound can be directed.

They sealed a loudspeaker into one end of a PVC pipe and secured the acoustic metamaterial to the opening on the other end and while testing the material, the team found that the acoustic metamaterial could block out nearly all sounds – 94 percent to be exact. This meant that the sounds left coming from the loudspeaker were imperceptible to the human ear.

The prototype of this metamaterial has proven so effective that the team is already looking at the practical applications and how it could make the world a quieter place. The implications for architecture and interior design are remarkable because these metamaterials could be applied to the built environment in many different ways. The researchers believe that HVAC systems could be fitted with these silencers, drones could have their turbines muted with such rings, even in MRI machines, which can be harrowingly loud for patients trapped in a small space, could be quieted.