Abstract
The primary function of noise barriers is to shield inhabitants of affected areas from excessive noise generated by road traffic. To enhance the performance of noise barriers while simultaneously adhering to height restrictions, the attachment of structures (caps) of different shapes to the tops of conventional screens can be considered. These caps can significantly impact the diffracted sound energy, thereby increasing the desired global acoustic losses. This work presents a comprehensive study of the acoustic performance of noise barriers with single and double attached caps of different shapes through a calculation of their insertion losses (IL). This study comprehensively addresses and compares different types, sizes, combinations, and numbers of noise barrier caps for different scenarios (including sloping and absorbent grounds) and sources (“car” and “ambulance”) for an extended frequency band up to 10 kHz. To the best of the authors’ knowledge, this is a range that has not previously been analyzed. A variety of different cap shapes were considered including cylinders, rectangles, trapezoids, and Y/T-shaped forms. To calculate the IL, an innovative and fast uniform theory of diffraction (UTD)-based method developed by the authors was applied in all simulations. The results showed that the Y-shaped single and double barrier caps were, in general, the most effective at increasing IL without raising the height of the barrier, thereby successfully managing the aesthetic impact. The results also showed how the consideration of sloping and absorbent floors could also contribute to improved noise abatement.
Highlights
The World Health Organization’s report on night-noise guidelines for Europe and the burden of disease from environmental noise affirms that about 20% of the European population is exposed to road traffic noise at levels exceeding 65 dBA [1]
To calculate the insertion losses (IL) in this study, an innovative, fast uniform theory of diffraction (UTD)-based method developed by the authors was applied in all simulations
The method implemented is based on an innovative two-dimensional (2-D or 2.5 D, if we take the ground reflection into consideration) formulation founded in UTD to analyze multiple diffraction/reflection of acoustic waves; the authors demonstrated, made comparisons, and validated such formulation in [43]
Summary
The World Health Organization’s report on night-noise guidelines for Europe and the burden of disease from environmental noise affirms that about 20% of the European population is exposed to road traffic noise at levels exceeding 65 dBA (equivalent sound pressure level [SPL] with A-frequency weighting) [1]. The above authors [21,22,23,24,25,26,27,28] typically analyzed single or multi edge-modified devices, but without systematically checking possible combinations of such structures and/or without extending the frequency range of evaluation further than 4–5 kHz. in this work, an extensive and comprehensive study of the acoustic performance of differently shaped single and double reflective structures (cap elements) attached to the top of conventional noise barriers was carried out by calculating their sound pressure insertion losses (IL). Sci. 2020, 10, x FOR PEER REVIEW consuming with other approaches such asit the boundary element method than 3000 frequency bins In this regard, should be mentioned that this(BEM). Materials and Methods authors; the with sameother extensive and painstaking would havemethod been extremely consuming approaches such as theanalysis boundary element (BEM). time-consuming with other approaches such as the boundary element method (BEM)
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