The control of airflow and acoustic energy for ventilation system in sustainable building

Abstract

Noise and air pollution problems become significant in a crowded city such as Hong Kong since buildings are usually close to the heavy traffic lines. Conventional window cannot fulfill all the functions of noise reduction, lighting and natural ventilation. New ventilated system, which combines the multiple quarter-wave resonators (silencer) with the new wing wall is designed to balance between acoustic and ventilation performances. Wind-driven natural ventilation is an effective way to preserve the safe and healthy indoor environment. The single-sided ventilation incorporated with wing walls could benefit from the dual flow ventilation mechanism and significantly increase the interior air circulation. Noise attenuation of the new ventilated window design improves significantly by combining flexible absorber and quarter-wave resonator effects. 10 dB to 22 dB transmission loss can be achieved in the frequency range between 500 Hz and 2 kHz band. The best ventilation performance of the wing wall is at an incident angle of 45°. Outlet air flow rate of ventilated window design is double of that of "the openable window". Rounded-inlet ventilated duct has effective performance in noise attenuation at any incident angle of the noise source. Even without combining with any acoustic absorptive materials, the noise reduction of ventilated duct can still much better than the conventional window. The ventilated duct has the acoustic effects similar to a standard expansion chamber with the extended inlet and outlet expansion chamber. The value of such a design is that part of the chamber between the extended pipe and the sidewall acts as a side branch resonator, therefore, improving the transmission loss. Computational simulation (CFD) and flow visualization technique in this research are verified by the results. The new design has effective acoustic and ventilation performance. The new natural ventilation design is an effective way in maintaining the comfort and health of the indoor environment.