Abstract: The mode superposition method is applied to compute the dynamic responses of a trough girder under urban rail transit trains based on vehicle-track-bridge interaction theory. The modal acoustic transfer vectors (MATVs) are obtained by using the SYSNOISE software. The structure-borne noise is then computed with the MATVs and the mode coordinates of the girder. The agreement between the calculated results and the measured ones in both frequency and amplitude demonstrates the reliability of the computational method. The peak frequencies of the structure-borne noise are found to be between 40Hz and 80Hz. The numerical results show that the excitations below 200Hz and the bridge modes below 100Hz can be used to compute the structure-borne noise with much high degree of accuracy. Only vertical contact forces between wheels and rails are required to simulate the noise numerically. The vibrations of the girder can be reduced effectively and the structure-borne noise can be reduced by 2dB-3dB through adjusting the stiffness of rubber pads under the rails. It is found that the sound pressure levels are obviously linear with the train speeds.