Membraned metasurface blocks noise but not air flow

Conventional windows must be open to circulate air with the outdoors but closed to block out noise, creating a dilemma for urban residences and offices that want fresh air without noise pollution.

To solve this problem, Zhang et al. designed and built a ventilated acoustic metasurface (VAM) that uses a membrane-type design to achieve both sound insulation and air flow. The VAM was especially good at blocking low-frequency and broadband noise, which have previously proved challenging to control.

The lightweight, compact VAM consists of an elastic membrane covered with sub-chambers of various depths. The authors explored the membrane-acoustic coupling for noise reduction in the low-frequency range. They found that when outdoor noise propagates through the VAM, the coupling between the soft surface of the membrane and air in the sub-chamber sends the sound waves back outside instead of allowing them inside.

“The proposed VAM has great potential for achieving interior silent ventilation windows, especially effective in low-frequency and broadband sound insulation,” said author Yingxin Zhang. “This research could be applied to windows in urban buildings or sound barriers at construction sites to achieve both sound insulation and ventilation performance.”

Next, the authors will use machine learning to optimize the metasurface’s ventilation and design, which they want to be thinner and more aesthetically pleasing. They also plan to explore the use of origami for the sub-chambers to eventually develop foldable ventilation windows and barriers whose sound insulation varies as origami structure changes.

Source: “Ventilated acoustic metasurface with low-frequency sound insulation,” by Yingxin Zhang, Yao Wei Chin, Xiang Yu, Milan Shrestha, Gih-Keong Lau, Boo Cheong Koo, Kun Liu, and Zhenbo Lu, The Journal of the Acoustical Society of America (2023). The article can be accessed at https://doi.org/10.1121/10.0020133 .