Boston University Researchers Develop ‘Smarter’ Sound Shield Blocking Noise Without Blocking Airflow
A new metamaterial design from Boston University promises a significant leap forward in noise control, offering broadband silencing while maintaining crucial airflow – a feat previously difficult to achieve.
A breakthrough from the Zhang Lab at Boston University is poised to revolutionize sound control technology. Led by Professor Xin Zhang (ME, ECE, BME, MSE), the team has published new research in Scientific Reports detailing a “Phase Gradient Ultra-Open Metamaterial” (PGUOM) capable of silencing a wide range of frequencies without impeding airflow. This advancement builds upon the lab’s long-running Acoustic Metamaterial Silencer project and addresses a critical limitation of earlier designs.
The Zhang Lab has established a reputation for translating cutting-edge research in metamaterials and microsystems into practical, real-world applications. Their initial work in 2019 focused on an “acoustic shield” designed to block sound using Fano resonance effects, primarily targeting narrowband noise reduction in systems like fans, propellers, and HVAC units. While effective, this approach was limited in its ability to address the complex and varied soundscapes found in many environments.
Recognizing this limitation, the team expanded its research to encompass multi-band, broadband, and tunable acoustic silencing strategies. This broadened scope makes the technology viable for diverse settings, including factories, offices, and public transportation hubs, where unpredictable sound frequencies and consistent airflow are paramount. The latest innovation, the PGUOM, represents a significant step toward achieving this versatility.
“PGUOM takes a smarter approach—more like noise-canceling headphones—effectively silencing a broadband of unwanted sounds,” explains Zhang. “It remains highly effective even as the noise shifts in pitch or volume, making it far more practical in dynamic settings like open offices, ventilation systems, or transportation hubs, where sound sources are unpredictable and span a wide range of frequencies.”
Earlier designs, based on Fano resonance, were likened to “tuning a radio to block a single station.” The PGUOM, however, offers a more comprehensive solution. The breakthrough relies on phase-gradient metamaterials, allowing for a customizable design that can adapt to specific application needs. The team has successfully created a ventilated PGUOM achieving broadband acoustic silencing with up to 70% openness.
The metamaterial’s structure is composed of repeating “supercells,” each containing three subwavelength unit cells. Solid barriers within the first and third cells induce controlled phase shifts in incoming sound waves, while the central cell remains open to ensure unobstructed airflow. These engineered phase shifts convert sound waves into “spoof surface waves”—acoustic analogs of electromagnetic surface plasmons—which are then trapped and dissipated, effectively suppressing broadband noise.
According to Zhang, the design’s adaptability is a key strength. “Our design isn’t one-size-fits-all—and that’s a strength,” she says. “It’s customizable in both frequency range and airflow level, depending on the application.” Unlike traditional phase-gradient structures, the central cell is enlarged to accommodate varying airflow requirements without sacrificing silencing performance.
The motivation behind this research extends beyond technological advancement. “Chronic exposure to excessive noise—often overlooked compared to air and water pollution—can seriously impact human health, contributing to hearing loss, sleep disruption, heightened stress levels, and even cardiovascular disease,” Zhang notes. The impact of noise pollution also extends to wildlife, disrupting ecosystems and affecting animal behavior. The team’s recent advances in lighter, more open, and broadband-capable materials aim to address these challenges on a larger scale.
The research has progressed beyond theoretical modeling, with the team successfully creating and testing physical prototypes. They are now focused on integrating the designs into specific products and optimizing the metamaterials for scalable manufacturing. “We’re also working to further enhance noise-blocking performance—aiming for high attenuation across even broader frequency bands, while preserving low airflow resistance and minimizing overall thickness,” Zhang adds.
Ultimately, the Zhang Lab is developing versatile and scalable solutions with the potential to create quieter, healthier environments across a wide range of industries.
More information:
Zhiwei Yang et al, Phase gradient ultra open metamaterials for broadband acoustic silencing, Scientific Reports (2025). DOI: 10.1038/s41598-025-04885-6
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