Boston University researchers recently developed an acoustic metamaterial that can silence sound without blocking airflow. The researchers claim to have designed the metamaterial based on mathematically perfect specifications.
For years, scientists have struggled with designing and finding the right materials to create a device to cancel noise completely. The nearest thing we have at the moment to full noise cancellation technology are noise-mitigating barricades or sound baffles.
While sound baffles can aid in drowning out normal noise, they are useless in situations where airflow is needed.
For instance, sound barricades can’t be used in stifling the noise coming from a jet engine’s exhaust vent. Instead, airport workers assigned on tarmacs use earplugs to minimize the noise and protect their ears from loud engine sounds.
In their paper, the Boston researchers claim that it’s possible to silence noise using their ring-like device.
Acoustic Metamaterial
The team relied on mathematics while designing their acoustic metamaterial. The dimensions and specifications of the metamaterial have been calculated to perfection, ensuring that it would only interfere with sound and not the flow of air.
The scientists sealed a loudspeaker on one end of a PVC pipe to test their invention. They then placed the acoustic metamaterial on the other end of the pipe. After setting up the loudspeaker and the ring-like device, the researchers played loud music through the loudspeaker but no sound came out.
Standing within the room and by relying on human hearing alone, one would not be able to guess that the loudspeaker was actually playing high-pitched music. The only sign that sound was coming out of it was the thrumming of the subwoofers seen when you peek into the PVC pipe.
The study’s co-author, Jacob Nikolajczyk, said in a statement:
“The moment we first placed and removed the silencer…was literally night and day. We had been seeing these sorts of results in our computer modeling for months—but it is one thing to see modeled sound pressure levels on a computer, and another to hear its impact yourself.”
According to the researchers, the shape of their acoustic metamaterial is customizable. Meaning, it doesn’t have to be round for it to work. The team believes that the potentials of their device are limitless, considering that it could be customized to fit any environment virtually.
“The idea is that we can now mathematically design an object that can block the sounds of anything.”
~ Xin Zang, Boston University, College of Engineering
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