Imagine a device that can block annoying noise—like that from fans, air conditioners, or busy offices—without stopping the flow of fresh air.
A research team at Boston University, led by Professor Xin Zhang, has invented exactly that.
Their latest work on advanced sound-silencing materials could soon help create quieter, healthier spaces in everything from office buildings to factories and public transportation hubs.
The innovation builds on years of research from the Zhang Lab, known for developing “acoustic metamaterials”—special materials designed to control sound in smart ways.
Back in 2019, they introduced a promising prototype called the Acoustic Metamaterial Silencer, which could block specific sounds while allowing air to pass through. This was a major step forward in noise control, particularly for fans and ventilation systems.
Now, the team has taken things much further. Their newest development is called the Phase Gradient Ultra-Open Metamaterial, or PGUOM for short.
It doesn’t just block one type of noise—it works across a wide range of sounds, including those that shift in pitch or loudness, which makes it far more practical in real-world settings.
At the same time, it allows for up to 70% airflow, which is crucial for spaces that need ventilation.
Professor Zhang compares the new system to noise-canceling headphones.
While earlier designs were like tuning a radio to block a single station, PGUOM is more like silencing everything you don’t want to hear. It can handle the unpredictable, varied noises that come from machines, human activity, and transportation systems.
What makes this technology so effective is its structure. Each part of the PGUOM is made from repeating “supercells,” which contain smaller units that guide how sound waves move through the material.
Some sections of each supercell block sound and bend it in precise ways, while the center stays open to let air flow freely.
These phase shifts cause incoming sound waves to be transformed into surface waves that get trapped and slowly die out, rather than bouncing around and causing more noise.
What’s exciting is that this isn’t just theory.
The Boston University team has already built physical prototypes, and they’re working to adapt the design for different uses. Whether the goal is to make HVAC systems quieter or reduce industrial noise in a factory, the design can be customized to the needed sound range and airflow requirements.
Zhang points out that excessive noise is more than just an irritation. It can seriously affect our health, leading to hearing problems, stress, poor sleep, and even heart issues.
Wildlife also suffers—animals rely on sound for communication and navigation, and noise pollution can throw entire ecosystems out of balance.
With this new sound-blocking technology, the team hopes to tackle both human and environmental noise challenges. Their next steps include improving performance even further, reducing thickness for easier installation, and preparing the material for large-scale manufacturing.
The ultimate goal? A world that’s quieter, more peaceful, and better for both people and the planet.
