高架轻轨噪声预报模型及实验对比

城市高架轻轨在缓解交通压力的同时也给其周边的环境带来了噪声问题。因此，其噪声预报开始逐渐受到技术人员的广泛关注。在前人研究的基础上提出一个轨道交通噪声沿水平方向传播的计算模型，把通过的列车看作一有限长线声源，将声场分为声影区和声照区。该模型不仅考虑了直达声的影响，还附加考虑声照区内的地面反射声、声影区内桥面与地面间的混响声以及地面振动引起的二次辐射声的贡献。为了验证理论模型的有效性，对上海市某高架轻轨运行段进行实测，测试与计算结果的趋势保持一致。通过不同模型计算结果与实测值的比较可见：在近场区增加混响声、地面反射声和地面辐射声，修正后的预报结果误差明显减小；在远场区，三种修正的影响随距离的增大而减小，因为声场趋于自由场。因此，所提出的预报模型可以作为高架轻轨声学设计参考。

Model for Prediction of Elevated Light-rail’s Noise and Experimental Verification

Although the urban light rail can ease public transportation pressure, it leads to the environment noise problems of the surrounding zone. Therefore, the noise prediction began to gain the attention of the technical staff. In this paper, an improved light rail noise calculation model is put forward on the basis of previous research. The model regard the train as a line source, and sound field is divided into sound shadow zone and sound direct zone. The model not only contains the impact of the direct sound, but also take the following factors into consideration: the ground-reflected sound (mainly in the sound direct zone), the reverberant sound between the bridge and the ground (mainly in the sound shadow zone), and the secondary sound radiation caused by the ground vibration. In order to verify the correctness of the theoretical model, some experiments have been done along certain light rail running route, and it can be found that the trend of test results are consistent with the calculation ones. By comparing the experiment results and the calculation ones, it can be found that in the near-field region, the forecast error is significantly reduced after the model including the reverberant sound, the ground-reflected sound and the ground-radiated sound. Besides, in the far-field region, the impact of three kinds of sound decreases with the distance, and the sound field tends to the free field. Therefore, the modified model presented in this paper can be used as a more accurate prediction model to guide the acoustic design of the light rail.