Abstract:To reduce the influence of wheel-rail noise on the area along the metro railway on the ground, active noise barriers were arranged near the metro track. The low-frequency noise could be significantly reduced by the active silencing system, and the high-frequency noise could be significantly reduced by the noise barrier. To guide the design of active noise barrier, the influence of secondary source parameters on metro noise field was studied. Based on the boundary element theory, a semi-free field model consisting of train, noise barrier and track was established. The correctness of the model was verified based on the measured data of Beijing Metro Line 13. The secondary sources were then arranged in the model along the longitudinal direction of the track with equidistance. By analyzing the numerical results, the most reasonable position of secondary sources, the silencing frequency, the silencing area boundary, and the silencing quantity were determined. A mathematical model of secondary sound interfering with noise was constructed to verify the rationality of the simulation conclusions. Results show that the most reasonable position of the secondary sources and the track axis were separated by a noise wave length. The height of the most reasonable position of the secondary sources was equal to that of the noise source. The most reasonable position of the secondary sources had a longitudinal interval shorter than half the noise wave length. Secondary sound could significantly reduce the wheel-rail noise of 150-320 Hz, and there was a positive correlation between silencing area and frequency. The silencing effect of bilateral secondary source array arranged on left and right sides of the train was better than that of unilateral sources arranged on one side. Setting secondary source arrays on the basis of noise barriers could generally decrease the total sound pressure level (SPL) in the sound shadow area by 3-12 dB, and the amplification value outside the sound shadow area basically did not exceed 3 dB, and the sound field in the train had little change.
