Study on noise insulation using double layered acoustic gratings

Noise reduction technologies that enable natural ventilation have garnered significant attention, especially in densely populated cities like Hong Kong and Singapore. These technologies not only provide aural and thermal comfort but also serve as alternatives to air conditioning during cooling seasons, thereby reducing energy consumption in green buildings. Common passive solutions for noise reduction and natural ventilation include plenum windows, coiling-up-space structures, and Helmholtz resonator (HR)-based structures. However, achieving effective noise isolation, particularly at low frequencies, often involves trade-offs, such as larger spacing between glass panels in plenum windows or increased volumes in coiling-up-space and HR-based structures, which can make them bulky and limit their practical applications. To overcome these challenges, we propose an ultrathin solution: the double-layered acoustic grating (DLAG). This innovative structure features two layers of rigid panels with perforated slits. Unlike noise insulation technologies that rely on energy conversion or impedance mismatch, the DLAG redirects acoustic energy away from sensitive areas, creating a quiet zone where needed. Additionally, the slit configuration supports natural ventilation. This paper will examine the noise reduction performance of the DLAG, specifically investigating its potential for low-frequency noise isolation.