Prediction and enhancement of the sound transmission loss across plenum windows

Abstract

Noise pollution is an emergent issue to be solved especially in developed cities, as it brings many health problems to citizens, such as high stress level, hypertension, tinnitus etc. Much efforts have been made for the noise control devices, for instance, noise barrier, extended podium, public parks, balconies, plenum windows. Plenum window is an interesting noise reduction device which can provide significant noise attenuation while maintaining a degree of ventilation. Despite the growing popularity of the plenum window, the prediction of its sound transmission loss is not straightforward. This study firstly tries to proposal a prediction model for the transmission loss across the plenum window. Besides, experiments were carried out for the validation of this empirical prediction models. Total of three prediction models were raised for the transmission loss of single plenum window and the second model gives the best prediction of all by comparison. It was also found that the diffracted field and reverberant field inside the plenum window form the theory were weaker than actual experiments. Based on the first part of study, extensive traffic noise transmission loss measurements were carried out inside the residential units of a standalone 30-storey housing block located in an opened environment next to a very busy and noisy main trunk road. Then the prediction and experiment models for the transmission loss of coupling plenum windows and three plenum windows were developed. Results show that the corresponding predictions agree very well with site measurement results. Besides, lab measurements and simulation was performed on the transmission loss of plenum window installed with rigid cylinder array. Parameters of diameter of rigid cylinder, rigid cylinder array types and gaps of the plenum windows were investigated in present study. Results show that the installment of rigid cylinder array inside the central cavity of the plenum window is effective and can provide significant acoustic protection.