US EditionHKU Engineers Find Physics Principle That Breaks Sound Absorption Limits
The team achieved over 86% broadband sound absorption from 300 Hz to 6000 Hz using duality symmetry, enabling airflow while reducing noise beyond previous theoretical limits.
- On 22 Feb 2026, Professor Nicholas X. Fang's HKU team published in Nature Communications identifying duality symmetry as key to new limits for ventilated sound absorbers.
- Ventilated systems traditionally allow airflow but let sound escape, while foam sound absorbers block ventilation; the causality constraint imposed a thickness–bandwidth limit based on one-port assumption, overlooking duality symmetry.
- Using a two-chamber ventilated resonator, the team designed two connected acoustic chambers and applied artificial intelligence and advanced simulations, recording over 86% absorption from 300 Hz to 6,000 Hz with a new Figure of Merit.
- Potential applications include quieter buildings, improved aircraft noise control, and damping solutions, with Acoustic Metamaterials Group Ltd. supporting tech transfer from the patent-rich lab of Professor I. David Abrahams.
- The study uncovers a deep mathematical coupling between duality symmetry and absorption bandwidth, revealing previously untapped absorption potential in broadband acoustic metamaterials presented at Phononics 2025 conference.
6 Articles
6 Articles
Engineers discover new physics principle to break sound absorption barriers in ventilated spaces
In everyday life, designing spaces that both let air flow and absorb sound can be a tricky balancing act. Usually, materials that allow air to pass through—like vents—also let sound escape, making it hard to reduce noise effectively. Conversely, sound-absorbing materials like foam often block airflow, limiting their use in ventilated areas.
Generalized causality constraint based on duality symmetry reveals untapped potential of sound absorption - Nature Communications
Causality constraints are known to bind sound absorption to a limit that can only be achieved by optimizing the system bandwidth for a specific material thickness. This limit is defined on the assumption of a one-port system, generally causing duality symmetry to be overlooked. Here, we define a generalized causality constraint of sound absorption by investigating reflection and transmission of a two-port hybrid monopole-dipole resonator. With o…
HKU Engineers Discover New Physics Principle to Break Sound Absorption Barriers in Ventilated Spaces - All News
Figure 1: The research team from The University of Hong Kong presented their findings at the Phononics 2025: 7th International Conference on Phononic Crystals/Metamaterials, Phonon Transport, Topologi...
Generalized causality constraint based on duality symmetry reveals untapped potential of sound absorption
Causality constraints are known to bind sound absorption to a limit that can only be achieved by optimizing the system bandwidth for a specific material thickness. This limit is defined on the assumption of a one-port system, generally causing duality symmetry to be overlooked. Here, we define a gen …
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