Designing spaces that are both well ventilated and quiet has always been difficult.
Openings that allow fresh air to circulate—such as vents and ducts—also let noise pass through.
Meanwhile, materials that absorb sound, like thick foam panels, often block airflow. This trade-off has limited how engineers control noise in buildings, vehicles, and machinery.
Now, a research team led by Professor Nicholas X. Fang from the University of Hong Kong has found a way around this problem.
Working with collaborators from the University of Cambridge and an industry partner, the scientists discovered a new physics principle that could change how ventilated sound barriers are designed.
Their study was published in the journal Nature Communications.
The breakthrough centers on a concept called duality symmetry, a mathematical idea originally developed in theoretical physics.
The researchers found that this principle determines how effectively a ventilated structure can absorb sound across different frequencies. Until now, symmetry and sound absorption were not thought to be directly connected. The team’s work reveals that they are deeply linked.
Using this insight, the engineers created a new type of sound-absorbing structure that still allows air to flow freely.
The design consists of two connected acoustic chambers. As sound waves enter the system, they interact in a way that causes destructive interference, meaning the waves cancel each other out and lose energy. This process traps and dissipates the noise while leaving the airflow largely unaffected.
In laboratory tests, the material performed remarkably well. It absorbed more than 86 percent of sound across a wide range of pitches, from low rumbling tones to higher frequencies. It also outperformed conventional foam panels of the same thickness. To evaluate the design fairly, the researchers developed a new measurement called a “figure of merit,” which considers sound absorption, airflow, and material thickness together.
For decades, engineers have relied on a rule known as the causality constraint, which suggests that thin materials cannot absorb sound across a wide frequency range. The new study challenges this assumption for ventilated systems. By applying duality symmetry, the team showed that it is possible to break these traditional limits and design materials that are both thin and highly effective.
The potential uses for this technology are wide-ranging. It could help create quieter homes and offices without sacrificing fresh air. It may also improve noise control in aircraft engines, factories, and transportation systems. Because the design can be optimized using artificial intelligence and computer simulations, the researchers believe it could be adapted for many different environments.
This discovery shows that solutions to everyday engineering problems can come from unexpected areas of physics. By combining advanced mathematics with practical design, the team has opened the door to quieter, more comfortable spaces where people can breathe easily without being disturbed by noise.
