高架轻轨箱梁噪声辐射现场实测分析
Measurement of noise radiated from box girder of elevated light rail transit

对武汉轻轨一号线某高架段25 m跨单箱单室预应力钢筋混凝土简支箱梁的噪声辐射进行了现场测试。将采集的噪声信号利用快速傅里叶变换技术通过相干函数进行一定程度的净化，从而获得真实的结构辐射噪声。绘制了箱梁结构表面辐射声压级等值线图。比较分析了综合噪声和结构辐射噪声的A声级。分析结果表明：近轨时箱梁结构各部位的辐射噪声明显大于远轨时箱梁结构各部位的辐射噪声。在近轨和远轨两种工况下，底板和翼缘的辐射噪声都大于腹板。箱梁各部位的辐射声压级在跨长方向和桥宽度方向上都表现出非单一的变化规律，需结合列车运行工况具体分析。轻轨箱梁结构辐射噪声级在61～66 dB（A）之间，实际工程中为了获得真实的结构辐射噪声级需将测得的综合噪声级减去约2 dB（A）（背景噪声影响）。实测分析结果可让工程技术人员了解箱梁噪声辐射情况，为后期箱梁的降噪设计提供参考依据。
In an elevated section of Wuhan light rail Line 1, a field test of the noise radiation has been made for the prestressed reinforced concrete simply supported box girder with a 25 m span of single box and single chamber. By using the Fast Fourier Transform (FFT) technique, the noise signal is purified to some extent by the coherence function so that the real structural radiation noise can be acquired. The contour maps of radiated sound pressure level from the surface of box girder are drawn and the A-weighted sound pressure levels of overall noise and structural radiation noise are compared and analyzed. The results show that for near rail the radiation noise from each part of box girder is significantly greater than that for distant rail. In these two conditions of near rail and distant rail, the radiation noises from bottom plate and flange plate are all greater than from web. The radiated sound pressure levels at diffident parts of box girder show different changing rules along the long span and bridge width, which should be analyzed according to the operation conditions of the train. The radiation noise of light rail box girder is between 61 dB (A) and 66 dB (A), and the 2 dB (A) influence of background noise should be deducted from comprehensive noise in order to obtain real structural radiation noise. The analysis of the measurement result can help engineers comprehend the noise radiation from the box girder, and provides a reference for the noise reduction design of the box girder.