Abstract
Four sets of numerical models were created to study the effects of shapes, staggering patterns, Helmholtz resonators and array configurations on the acoustical performance of sonic crystals (SCs) in order to design an efficient SC window to mitigate the traffic noise level at a room in a student hostel of NUS. Rectangular SCs consistently obtained highest transmission loss for frequencies ranging from 300 Hz to 3000 Hz compared to diamond and semi-circle SCs. Fully staggered pattern performed better than non-staggered and 50 % staggered patterns for frequencies below 1700 Hz. Helmholtz resonators were useful for enhancing low frequency noise mitigation. The prototype of the final designed SC window was fabricated and tested in order to validate the simulation result. Generally, numerical and experimental results were in similar trends. Maximum transmission loss of the SC window was found to be occurred at 900 Hz which was about 18 dB.
Highlights
The idea of sonic crystal (SC) appeared in the 90s and it was defined as periodic distribution of cylindrical sound scatterers in air to inhibit sound transmission by their acoustic band gaps [1]
It can be concluded that Helmholtz resonators are useful for low frequency noise mitigation which might not be able to solve by conventional solid SCs due to the limitation of space
Four sets of numerical models were created to study the effects of shapes, staggering patterns, Helmholtz resonators and array configurations on the acoustical performance of SCs in order to design an efficient SC window to mitigate the traffic noise level at a room in a student hostel at NUS
Summary
The idea of sonic crystal (SC) appeared in the 90s and it was defined as periodic distribution of cylindrical sound scatterers in air to inhibit sound transmission by their acoustic band gaps [1]. The performance of the SC noise barriers which composed of infinitely long multi-resonant composite scatterers was investigated by Krynkin et al [6] through experimental and theoretical methods They found that the use of the resonating elements in SCs resulted in effective sound mitigation in the low frequency range and the SCs still preserving the existence of the Bragg band gap. Koussa et al [11] evaluated the acoustical performance of a noise reducing device which combined SCs with a conventional noise barrier using 2D Boundary Element Method (BEM) Their results showed a significant transmission loss due to the addition of the SC elements for middle and high frequencies of typical road traffic noise. The initial prototype of the SC window was fabricated and tested in a corridor first before the actual installation at student hostel to validate the simulation result
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