Noise Reduction Effect Testing and Analysis of Vertical Sound Barriers in Elevated Urban Rail Transit Sections

［Objective］ Sound barriers are widely used in elevated sections of urban rail transit. However, studies on their actual noise reduction performance during operation remain limited. Therefore, it is necessary to investigate the noise reduction effectiveness of vertical noise barriers in real operation conditions and analyze the characteristics and distribution patterns of noise. ［Method］ Using the sound barriers of Ningbo Rail Transit Line 1 as the engineering background, measuring points are placed at different heights (2 m, 3 m, and 4 m) on vertical sound barriers. Noise levels are monitored as trains passing these points, and the acoustic characteristics such as sound pressure level spectrum and insertion loss are analyzed. ［Result & Conclusion］ The noise energy generated by train operation is distributed over a broad frequency range, with dominant frequencies between 500 Hz and 800 Hz near the primary noise sources. Within the acoustic shadow zone of the sound barriers, lower measurement points exhibit better noise reduction effects. The sound barriers are more effective at attenuating high-frequency noise than low-frequency noise. At a distance of 7.5 m from the track centerline, the average noise reduction values in the acoustic shadow zone for 2 m, 3 m, and 4 m high vertical sound barriers are 4.0 dB (A), 6.7 dB(A), and 11.1 dB(A), respectively.