城市高架轨道桥辐射噪声的计算与分析

为采取合适的噪声控制策略提供依据,预报城市高架轨道桥辐射噪声场很有必要.基于一个简化两维模型,考虑各种变化因素(两旁建筑物高度、间距等)的影响,应用边界元方法对进行了噪声场和频谱的计算预测,通过与实际测量数据的对比分析,结果表明:噪声的低频成分(＜250Hz)主要由桥体结构振动辐射产生,而轮轨振动辐射是较高频(250～1000Hz)噪声的重要来源;低频噪声场上下明显强于两侧,而随频率的增高,声场混响特征增强.结论是:对于噪声不便于测试的高架桥这样大型结构,边界元方法能够有效预报噪声场,高架桥两侧声屏障可以取得5-10分贝的隔声效果,为防止上部出现噪声过大的情况两侧建筑物需要适当的高度/距离比.

Numerical Prediction and Analysis of Radiated Noise from Viaduct of City

Predicting the noise radiation from city viaduct in advance is necessary for suitable disposition of noise controlling strategy. Applying boundary element method, the noise field and spectrum are numerically predicted for a simplified two-dimension model of city viaduct under variant surroundings. Numerical result by comparison with the tested data reveals that: noise radiation at frequencies below 250 Hz is mainly due to viaduct vibration, and noise of higher frequency comes dominantly from the track-wheel interaction emission. It also shows that noise levels above or beneath the viaduct are obvious higher than those on two sides at low frequency, and noise filed possesses stronger reverberant feature as frequency goes higher. It is concluded that: for inconvenient measured noise field from large structures like city viaduct, boundary element method is an effective tool to predict noise field below frequency 1000 Hz;Using sound barrier for viaduct can reduce noise level about 5 to 10 decibel; Reasonable ratio of distance to height is needed for side buildings to prevent unexpected high noise level on the surface of their upper parts.