15 m. The sound leakage has an obvious influence on the soundinsulation properties of noise barriers, especially at high frequencies. Therefore, a sealing treatment is indispensable in the actualnoise barrier.5. ConclusionsOn the basis of the SEA, a model of the vertical noise barrier wasestablished to predict its noise reduction performance in the frequency domain during the passing of a train on the railway bridge.Two sub-models were built to estimate the TLs between the elementplates and the cavities as well as those between the two cavities tosimulate isolation properties and sound absorption. A field measurement was conducted on a simply supported box girder railwaybridge, which was used to determine the rules of noise distributionon the transverse plane and validate the simulation results. Furthermore, the factors affecting the vertical noise barrier were explored.The following conclusions were drawn from this study:(1) The noise in the sound field of the open and closed sides wasmeasured at the corresponding positions, which were coincident in the time domain and had a wide distribution inthe frequency domain. The attenuation of the overall SPLson the closed side was approximately 33 dB(A) and 36 dB(A) at points 7.5 m and 15 m away from the central line ofthe rail track, respectively.(2) The numerical models developed in this study to predict thenoise reduction performance of the vertical noise barrierwere accurate and effective. The loss factors of the subsystems are the most important parameters in the SEA model.The overall insertion losses of the vertical noise barrier wereapproximately 12 dB(A) and 11 dB(A) at points 7.5 m and15 m away from the central line of the rail track,respectively.(3) The noise reduction effect of the barrier was deeply influenced by its height, while increasing the height of the barrierindiscriminately may not be the most effective way. Installing fence top and a sealing treatment are excellent in noisebarrier optimization, while cooperating with internal soundabsorption materials can achieve better improvement.Therefore, a comprehensive consideration of various aspectsis necessary in the construction of a vertical noise barrier