【Objective】To address the significant difference of interior noise between the motor car (M car) and the trailer (T car) during the operation of an urban rail vehicle, this research examines the impact of the motor car's traction drive system on interior noise through a combination of numerical simulation and real-world vehi cle testing. 【Method】Initially, spectral responses and transmission characteristics of the vibration and noise with in and outside the car body of both the motor car and the trailer were analyzed based on test results. Subsequent ly, a full-frequency vehicle interior noise simulation model was developed by integrating the statistical energy method (SEA) and the finite element method (FEA) for numerical simulation purposes. The simulation revealed the distribution patterns of high-frequency airborne sound and low-frequency structural sound within the vehicle. Through computational superposition of structural and airborne sound, comprehensive noise distribution charac teristics across the full frequency band were obtained and compared with corresponding measured data from the rail line. 【Result】The results show that a prominent peak exists in the interior noise of the motor car within the frequency range of 150 to 400 Hz, which corresponds with the vibration peak of the floor structure within the vehi cle. 【Conclusion】The simulation outcomes of the low-frequency structural acoustic model of the vehicle exhibit a high degree of consistency with the actual measured data. The high-frequency noise within the vehicle is pri marily attributed to wheel-rail rolling noise and the airborne acoustic propagation path of the traction system's sound source. The peak noise levels in the motor car are a result of structural vibrations from the traction drive system, which includes the motor and gearbox, being transmitted through the frame and secondary suspension components to the vehicle body structure, leading to increased levels of low-frequency structural noise. These findings may provide some reference for mitigating the impact of the traction drive system on the interior noise of urban rail vehicles.