Abstract
In the present study, a conventional plenum window was incorporated with perforated thin box in order to enhance its performance at frequency range which centralized at 1000 Hz as most of the common noise sources at city nowadays are centralizing around this frequency. The entire studies were conducted in a reverberation room. The effectiveness of jagged flap on mitigating diffracted sound was also studied. Three types of noises were examined in the current study—white noise, traffic noise and construction noises. The experimental results showed that the plenum window with perforated thin box could reduce 8.4 dBA, 8.7 dBA and 6.9 dBA of white, traffic and construction noises, respectively. The jagged flaps did not have significant effect on the plenum window’s noise mitigation performance. When frequencies were ranging from 800 Hz to 1250 Hz, when compared with the case of without perforated thin box, it was found that the perforated thin box had good acoustic performance where it was able to reduce additional 1.6 dBA, 1.6 dBA and 1.2 dBA of white, construction and traffic noises, respectively.
Highlights
According to the definition from Ford and Kerry [1], the outer and inner openings of a plenum window are staggered in order to prevent sound passes through it directly
When frequencies are ranging from 20 Hz to 5000 Hz, ∆LAeq1 that obtained by the plenum window with perforated thin box is shown in
Conventional plenum window was incorporated with perforated thin box in order to enhance its performance at frequency range which centralized around 1000 Hz
Summary
According to the definition from Ford and Kerry [1], the outer and inner openings of a plenum window are staggered in order to prevent sound passes through it directly. Li et al [9] inside the building acoustics testing chambers of the Hong Kong Polytechnic University in an attempt to develop a simple empirical prediction model for the traffic noise transmission loss across plenum windows Their results showed that a model which assumed frequency-independent diffraction directivity and percentage reverberant field attenuation gave the best prediction of traffic noise transmission loss. It can be seen that plenum window is more reliable for practical application compared to noise barrier because it still allows air to pass through its gap while it is fully staggered. It is transparent and it can be installed on the window frame of a residential unit. In the present study, since sound diffraction might be occurred over the gap or edge of the plenum window’s glass pane, jagged flaps with different angles were installed on the edge of the glass pane in order to reduce the energy of the diffracted sound
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