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Upward refraction of sound propagating outdoors by a graded index sonic crystal noise barrier

机译：渐变折射率声晶体噪声屏障向上传播到室外的声音

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摘要

Upward refraction of sound propagating outdoors by a finite set of two-dimensional cylinders has been studied in the homogenization region. All cylinders in the field are located above a ground plane and have their longitudinal axes orientated parallel to the ground. By increasing the cylinder radius with height, a graded index medium is created whose effective sound speed decreases over height. A cylindrical wave propagating inside a structure obeying such properties can be refracted upwards, consequently creating a zone of reduced pressure behind it. Acoustic phenomena for continuous graded index media (GRIN CM), predicted using the Finite Element Method (FEM), are demonstrated. Using modified homogenization formulas the results are then matched with a qualitatively equivalent graded index sonic crystal (GRIN SC), predicted with Multiple Scattering Theory (MST). It is shown that GRIN SC noise barriers potentially can be effective as broadband noise mitigation measures, with a barrier setup filling a cross sectional area not bigger than two meter squared. However, in order to gain a reasonable insertion loss, the barrier thickness must be chosen in accordance with the wavelength of the incoming field and should be in the order of a few wavelengths. Furthermore, the performance of these refractive structures is determined by the shape of the effective sound speed profile in relation to the point of excitation.
机译：在均质化区域，已经研究了有限的二维圆柱体在室外传播的声音的向上折射。现场中的所有圆柱都位于地平面上方，并且其纵轴平行于地面定向。通过随高度增加圆柱半径，创建了渐变索引介质，其有效声速随高度降低。遵从这种特性的在结构内部传播的圆柱波可以向上折射，从而在其后面创建一个减压区域。演示了使用有限元方法（FEM）预测的连续渐变索引介质（GRIN CM）的声学现象。然后使用修正的均化公式，将结果与定性等效的渐变折射率声波晶体（GRIN SC）相匹配，并用多重散射理论（MST）进行预测。结果表明，GRIN SC噪声屏障可以有效地用作宽带噪声缓解措施，其屏障设置可以填充不超过两平方米的横截面。然而，为了获得合理的插入损耗，势垒厚度必须根据入射场的波长来选择，并且应该在几个波长的数量级上。此外，这些折射结构的性能由有效声速曲线相对于激发点的形状决定。

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  • 来源
    《Applied Acoustics》 |2013年第1期|89-101|共13页
  • 作者

    Bart van der Aa; Jens Forssen;

  • 作者单位

    Department of Civil and Environmental Engineering, Division of Applied Acoustics, Chalmers University of Technology, SE-41296 Coteborg, Sweden;

    Department of Civil and Environmental Engineering, Division of Applied Acoustics, Chalmers University of Technology, SE-41296 Coteborg, Sweden;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    refraction; homogenization; outdoor sound propagation; GRIN CM; GRIN SC;

    机译：折射;均质化户外声音传播;GRIN CM;GRIN SC;

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