At a glance 2 min

A meta-material to end noise pollution

A meta-material to end noise pollution
A meta-material to end noise pollution

Whether at home, at the office or in the street, we all suffer from noise pollution to varying degrees. It can even become unbearable for some.
Researchers at Boston University are apparently close to solving this problem. They have developed a cylindrical meta-material* able to almost entirely reduce any noise attempting to pass through it.
This “acoustic meta-material” is shaped like a large, mathematically-designed and 3Dprinted synthetic ring able to capture certain frequencies passing through the air and reflect them towards their source. The advantage it offers is that air and light can pass through it, but not sound.

94% noise reduction

In order to test their invention’s effectiveness, the researchers placed a loudspeaker into a PVC pipe and the ring at the other end of the pipe to listen to the sound emitted. Although the volume was pushed to the limit, they heard nothing. The sound was successfully and completely blocked thanks to the small 3D-printed ring. It cut out 94% of the sound from the loudspeaker, enough to make it inaudible to the human ear.

Soundproofed walls

It is easy to imagine the many opportunities for such an innovative item, particularly in the field of architecture and interior design. While “Today’s sound barriers are literally thick and heavy walls”, said Reza Ghaffarivardavagh, one of the two researchers, acoustic meta-materials could be stacked to build transparent soundproof walls in offices. “Our structure is extremely lightweight, open and beautiful. Each ring could be used as a tile or a brick to build a permeable and silent wall.”

Ending noise pollution

The ring could also be used to reduce the noise made by medical imaging devices and ventilation systems. And why stop there? Vacuum cleaners, drill motors, airplanes, car and motorbike exhaust pipes could all be fitted with this “silencer”. There seems to be infinite variety of applications for this item! “The main outcome is that we are now able to mathematically design an object that can block any sound”, explained Xin Zhang, Professor at Boston University.

*In physics, in electromagnetism, the term meta-material refers to an artificial composite material which has electromagnetic properties not found in a natural material.*

Photo by Cydney Scott, Boston University

www.bu.edu/research/

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