Development of metacage for noise control and natural ventilation in a window system

Abstract

Ventilation window is one of the critical elements in sustainable building development, although frequently, outdoor factors such as environmental noise can limit their use. It is necessary to develop windows with both natural ventilation and noise mitigation functions. Acoustic Metamaterials (AMMs) set a new trend in solving physical challenges related to sound wave control, which can find their applications in ventilation window. This study presents a design based on acoustic metacage concept to enhance the window’s natural ventilation and acoustic performance. Finite Element Method (FEM) is used to study and optimise the acoustic performance of the metacage window. The ventilation is evaluated at the same time following predefined guidelines related to the window’s opening ratio and air-flow directivity. The metacage window structure finally, reduces the noise transmission with a mean value of 30 dB within a frequency range of 350–5000 Hz and has an opening ratio of the 33% compared to the whole system surface. The front panel gives a mean high frequencies TL contribution of 17 dB (2000–5000 Hz). Additional lateral constraint and cavities increase the TL performance up to 70% on a wider lower frequency range (350–5000 Hz). Thanks to the cavities, the resonant unit cells among the acoustic metasurface (AMS) significantly suppress sound from exiting the structure in broadband frequencies and allow bigger opening on the lateral side. This significantly contributes to the natural ventilation potential of the metacage window, which in the long term, becomes equally effective to the conventional open windows.