Enhancing ventilation window acoustics with sonic black hole integration: A performance evaluation

The inherent conflict between natural ventilation and noise reduction presents a significant challenge in building design. To address this issue, double-layer ventilation windows have been developed, but their acoustic performance remains suboptimal when the window is partially open. Recently, sonic black hole (SBH) structures emerged as promising acoustic devices to absorb sound waves. This study explores the incorporation of SBH structures to enhance the acoustic performance of double-layer ventilation windows. The investigation focuses on positioning SBH units inside the window cavity for sound absorption, and at the outlet of the window for sound isolation. The working principles and modeling techniques for designing SBH units are elaborated. Impedance tube tests are conducted to confirm the desired sound absorption and transmission loss properties of the designed SBH elements under plane wave incidence conditions. To predict the acoustic performance of the modified windows, numerical models are developed using finite element analysis. The results indicate that the incorporation of SBH units yields improved sound attenuation within the target frequency range specified by the SBH design, and the design approach demonstrates great tunability and potential for optimization. To validate the numerical predictions, a 1:2 scale model of the window was constructed, with individual SBH elements produced via 3D printing. Experiments conducted in an anechoic chamber confirm the noise reduction capabilities of various window configurations with integrated SBH elements, and the experimental results corroborate well the numerical simulations. This study introduces the novel application of SBH in ventilation windows, with preliminary findings indicating the potential benefits of SBH integration. Further optimization based on the design approach, numerical models, and experimental techniques established herein is warranted.