Sonic crystal noise barriers

室外隔音屏障用于减少来自固定工业厂房、飞机地面操作和道路的噪音干扰。近年来，人们对利用声波晶体作为噪声屏障的潜力越来越感兴趣。声波晶体因光子晶体对光的类似作用而得名。它们由圆柱体的周期性阵列组成，并且由于多次散射，已知在选择频率下具有高衰减。通过假设半波长的整数与散射体之间的距离相匹配，可以找到衰减最大的频率。声波晶体（sc）的主要优点之一是，通过改变圆柱体之间的距离，可以在一定频率范围内达到衰减峰值。SC势垒的一个优点是其相对的光学透明性。另一个可能是它对风的相对渗透性，从而减少屏障引起的湍流和风梯度增强的影响。原则上，如果SC屏障用作道路两侧的高速公路隔音屏障，则应该比固体屏障之间的混响更少。SC屏障的出现也可能具有相当积极的美学影响。毕竟，使用sc作为屏障的兴趣始于一个由垂直平行圆柱体组成的“雕塑”作为音障的发现。将考虑各种可能的SC屏障设计。除了“传统的”垂直圆柱体阵列外，反射面上的水平圆柱体阵列、椭球圆柱体阵列和弯曲圆柱体阵列的声学性能将通过分析/数值和实验室测量进行研究。优化设计的SC阵列利用声透镜效应和覆盖物将进行研究。运输研究实验室将测试适合道路交通噪音配置的垂直圆柱阵列的声学性能，并将其与不同风况下的简单屏障的声学性能进行比较。

Outdoor noise barriers are used to reduce noise disturbance from fixed industrial plant, from aircraft ground operations and from roads. Recent years have seen a growing interest in the potential for use of sonic crystals as noise barriers. Sonic crystals take their name from the analogous effects of photonic crystals on light. They consist of periodic arrays of circular cylinders and are known to give high attenuation at selective frequencies as a consequence of multiple scattering. The frequencies of highest attenuation can be found by assuming that an integer number of half wavelengths fits the distance between the scatterers. One of the main advantages of sonic crystals (SCs) is that by varying the distance between the cylinders it is possible to attain peaks of attenuation in a certain range of frequencies. One advantage of an SC barrier would be its relative optical transparency. Another would be its relative permeability to wind, thus reducing the effects of barrier induced turbulence and wind-gradient enhancement. In principle, if SC barriers are used as highway noise barriers on both sides of a road, there should be less reverberation than between solid barriers. The appearance of an SC barrier might also have a rather positive aesthetic impact. After all, the interest in using SCs as barriers started with the discovery that a 'sculpture' consisting of vertical parallel cylinders acted as a sound barrier. Various possible designs of SC barriers will be considered. In addition to 'conventional' vertical circular cylinder arrays, the acoustical performance of horizontal cylinders arrays above a reflecting plane, ellipsoidal cylinder arrays and curved arrays will be investigated both analytically/numerically and through laboratory measurements. The optimisation of the design of SC arrays making use of acoustic lens effects and coverings will be investigated. The acoustical performance of vertical cylinder arrays in configurations suitable for road traffic noise will be tested and compared with that of a simple barrier in various wind conditions by the Transport Research Laboratory.