Skip to main content

Scientists discover a strange shape that blocks almost all sound

We live in a loud world. Car engines, cellphones, pop music piped through grocery-store speakers — it can seem impossible to escape all the noise. Silence is a luxury.

But a new shape discovered by researchers at Boston University could help bring peace and quiet to our lives. Well, at least some quiet.

Called an “acoustic metamaterial,” the shape was developed based on a mathematically modeled design that enables it to cancel up to 94 percent of sound by reflecting certain frequencies back to their source.

“Acoustics is a very old field of research with a very rich history,” Reza Ghaffarivardavagh, a BU mechanical engineer who worked on the project, told Digital Trends. “The advent of new fabrication technologies and advancement in computational tools have helped us better understand and utilize the interaction of acoustic waves with complicated solid objects.”

Acoustic Metamaterial Noise Cancellation Device

Most sound barriers today include thick walls and acoustic panels. These techniques are effective, but they can be large, unwieldy, and aren’t fit for situations that require uninterrupted airflow.

That is why Ghaffarivardavagh and mechanical engineer Xin Zhang began to look for a technology that would preserve the passage of air but still block sound. Using mathematical modeling and 3D printing, they developed the acoustic metamaterial, which is capable of catching and reflecting the tiny disturbances in the air that cause sound. Typical acoustic panels capture sound rather than reflect sound like the acoustic metamaterial.

To test their invention, the researchers put a loudspeaker into one end of a large PVC pipe and placed the acoustic metamaterial at the other end. The metamaterial effectively silenced 94 percent of the loudspeakers sound — or, enough to make it practically imperceptible to the human ear.

The acoustic metamaterial may find uses in quieting things like HVAC units and drone turbines. “Our design is extremely open, cheap to fabricate, and lightweight,” Ghaffarivardavagh said. “I believe there are great opportunities for its application, such as decreasing noise from fans. Our silencer’s performance is a narrow band but we are working on the wider-band design along with a tunable model, which may open up new possibilities.”

A paper detailing the project was published this week in the journal Physical Review.

Editors' Recommendations

Dyllan Furness
Dyllan Furness is a freelance writer from Florida. He covers strange science and emerging tech for Digital Trends, focusing…
DARPA is developing an underwater GPS alternative that relies on sound waves
Underwater navigation sound waves help submarine location systems

On the ground, humanity relies pretty much entirely on GPS satellites to get real-time directions from point A to point B. But underwater, even the U.S. military can’t access GPS signals to navigate a charted course. That’s why DARPA is asking for proposals on an underwater acoustic system to replace heavy reliance on GPS. The Positioning System for Deep Ocean Navigation, which has been nicknamed Posydon, could be the key to more accurate underwater navigation.

GPS signals rely on high frequency radio waves to transmit their location data, but those waves can’t penetrate more than a few inches beneath the surface of the ocean. Submarines making long journeys are forced to surface while at sea in order to sync up with GPS satellites, which isn’t a viable option for subs executing stealth missions. In the absence of GPS, submarine personnel are forced to process complex calculations based on speed, distance, and direction, alongside environmental factors like ocean currents.

Read more
SoundCloud’s deal with Sony means access to tunes from all three major labels
soundcloud launches paid subscription service new berlin office

Music streaming service SoundCloud has signed a landmark deal with Sony Music Entertainment, giving it working agreements with all three major labels, according to The Verge.

The new deal is an important step towards the company’s upcoming paid subscription service, which is rumored to hit the public by the end of the year.

Read more
SoundCloud’s top charts help you discover hottest tracks, podcasts
soundcloud is losing big money ipad ios music service

Music streaming service SoundCloud is used by some of the biggest acts in the world to share tracks. For many users, however, the site isn’t as accessible and easily navigable as the likes of Spotify or Apple Music.

Thankfully, the introduction of charts to the service makes it a lot easier to discover the most popular new music and audio files, including audiobooks and podcasts.

Read more