Low-frequency noise inside metro: contribution analysis and noise control treatment

Low-frequency interior noise tends to tire passengers and affect their health, the wheel/rail vibration and rolling noise are crucial noise sources. For a metro vehicle, the wheel/rail vibration transmits to the car body through the primary and secondary suspensions, causes the car floor vibration, the wheel/rail rolling noise transmits to carriage. An original study tries to predict low-frequency interior noise and reveal the acoustic law of panel contribution and improve ride comfort combining a wheel/rail rolling noise model, a rigid-flexible vehicle-track coupled dynamic model and detailed car body structural/acoustic finite element models. The results show that, based on the acoustic transfer vector method, the critical element contribution areas to the low-frequency noise were found; after removing the impact of critical elements, the sound pressure level peak at 80 Hz and 110–200 Hz decreased. The thickness increase can improve sound insulation level, but change the lower natural frequency, improve the structure’s stiffness, suppress the amplitude of the transfer function. Based on element contribution analysis, the damping optimization method shows that the global SPL peak decreases by 4.3, 6.4, 7.8, 1.8, 3.5, and 5.2 dB (A,) respectively, from position 1 to 6.