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Still Waters

'Acoustic metamaterial' that cancels sound

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Still Waters

Boston University researchers, Xin Zhang, a professor at the College of Engineering, and Reza Ghaffarivardavagh, a Ph.D. student in the Department of Mechanical Engineering, released a paper in Physical Review B demonstrating it's possible to silence noise using an open, ringlike structure, created to mathematically perfect specifications, for cutting out sounds while maintaining airflow.

"Today's sound barriers are literally thick heavy walls," says Ghaffarivardavagh. Although noise-mitigating barricades, called sound baffles, can help drown out the whoosh of rush hour traffic or contain the symphony of music within concert hall walls, they are a clunky approach not well suited to situations where airflow is also critical. Imagine barricading a jet engine's exhaust vent—the plane would never leave the ground. Instead, workers on the tarmac wear earplugs to protect their hearing from the deafening roar.

https://phys.org/news/2019-03-acoustic-metamaterial-cancels.html?

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and then

A great leap forward for weapons sound suppression!  Once the cost comes down, of course :(  Imagine being able to practice at the range all day and not be encumbered by bulky headsets.  Cool!

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Celumnaz

That's like the cone of silence.  Cool.  So many applications.

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L.A.T.1961

On the plus side it looks cheap to make. Unfortunately it appears that it works at one fixed pitch only, so the design has to be altered if the sound frequency changes. 

OK if the sound you want to cancel is a single fixed pitch but for general multi tone noise almost completely ineffective.

Nice idea though. 

 

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Timothy
On 08/03/2019 at 1:09 PM, L.A.T.1961 said:

On the plus side it looks cheap to make. Unfortunately it appears that it works at one fixed pitch only, so the design has to be altered if the sound frequency changes. 

OK if the sound you want to cancel is a single fixed pitch but for general multi tone noise almost completely ineffective.

Nice idea though. 

To work effectively it would have to be smart and physically adapt real-time, akin to good noise cancelling headphones.

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