Let’s face it, life in the city is noisy. Car horns, the rumble of trains, air conditioners, sirens. Blocking out the din, however, typically requires barricades that restrict airflow.

But mechanical engineering professor Xin Zhang and her colleagues have come up with a solution.

Leaning on their mathematical prowess and the technology of 3-D printing, the researchers argue it’s possible to silence noise using an open, ring-like structure, created to mathematically perfect specifications, for cutting out sounds while maintaining airflow.

In a January 2019 Physical Review B paper, they demonstrated that such a feat was possible by developing a material with unusual and unnatural properties (known as a metamaterial), in this case with the ability to exert an isolated influence on sounds—an acoustic metamaterial. In fact, their experimental “sound baffles” canceled 94 percent of noise.

This has huge implications for the commercial sector. Companies like Amazon could mute their future delivery drones, keeping their customers—and neighbors—happy. Fans and HVAC systems could run silently yet allow hot or cold air to circulate unfettered throughout a building.

It’s no surprise that Zhang’s pioneering work has attracted attention from numerous private companies and also earned her BU’s Innovator of the Year award in 2018.

“If you ask me and my colleagues, acoustic metamaterials are the future,” Zhang says.

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