Abstract Current models for the acoustic radiation from railway wheels assume free field radiation. However, slab tracks are increasingly used for new railway lines. The acoustically hard surface of those tracks makes a re-evaluation of the free field assumption relevant, as such a surface can affect the radiation efficiency of an acoustic radiator. The wheel as the acoustic radiator is most conveniently described in a cylindrical coordinate system, thus making use of its axisymmetry. While this is a viable solution for the structural vibrations, for instance by using the curved Waveguide Finite Element formulation, the axisymmetry breaks when including a reflective plane in the calculation of the acoustic radiation. A convenient method to include an infinitely large, reflective plane is by using half-space Green’s functions in combination with the Boundary Element method. This method can be formulated in cylindrical coordinates using the Fourier series BEM (FBEM). However, the FBEM has not yet been combined with half-space Green’s functions. This paper provides a half-space formulation for the FBEM, which enables e.g. the evaluation of sound radiation of railway wheels over reflective surfaces. Finally, it is shown that the assumption of free field radiation for railway wheels is valid, as there is no major contribution of the reflective plane to the radiation efficiency of the wheel. The developed method is validated against laboratory measurements as well as analytical models.

中文翻译：

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来自铁路车轮的声音辐射，包括地面反射：傅立叶边界元方法的半空间公式

摘要 铁路车轮声辐射的当前模型假设为自由场辐射。然而，新铁路线越来越多地使用板式轨道。这些轨道的声学硬表面使得重新评估自由场假设相关，因为这样的表面会影响声学辐射器的辐射效率。作为声辐射器的轮子最方便地在圆柱坐标系中描述，从而利用其轴对称性。虽然这是结构振动的可行解决方案，例如通过使用弯曲波导有限元公式，但在声辐射计算中包括反射平面时，轴对称性会中断。一种包括无限大的方便方法，反射面是利用半空间格林函数结合边界元法。可以使用傅立叶级数边界元法 (FBEM) 在柱坐标系中制定此方法。然而，FBEM 尚未与半空间格林函数结合。本文提供了 FBEM 的半空间公式，例如，它可以评估铁路车轮在反射表面上的声辐射。最后，表明铁路车轮的自由场辐射假设是有效的，因为反射面对车轮的辐射效率没有主要贡献。所开发的方法经过实验室测量和分析模型的验证。FBEM 尚未与半空间格林函数结合。本文提供了 FBEM 的半空间公式，例如，它可以评估铁路车轮在反射表面上的声辐射。最后，表明铁路车轮的自由场辐射假设是有效的，因为反射面对车轮的辐射效率没有主要贡献。所开发的方法经过实验室测量和分析模型的验证。FBEM 尚未与半空间格林函数结合。本文提供了 FBEM 的半空间公式，例如，它可以评估铁路车轮在反射表面上的声辐射。最后，表明铁路车轮的自由场辐射假设是有效的，因为反射面对车轮的辐射效率没有主要贡献。所开发的方法经过实验室测量和分析模型的验证。因为反射面对车轮的辐射效率没有主要贡献。所开发的方法经过实验室测量和分析模型的验证。因为反射面对车轮的辐射效率没有主要贡献。所开发的方法经过实验室测量和分析模型的验证。