Study On The Cause Of Abnormal Noise In The Cab Of A Metro Train

In recent years, China's urban traffic congestion, air pollution, noise pollution, resource shortage and other issues have become increasingly prominent,In order to alleviate the above problems, the major cities have built subway and other urban rail transit, Chengdu as the largest city in the southwest, four subway lines have been built since 2005, is expected by the end of 2020 to achieve the opening mileage of 500 km, which will greatly reduce the traffic pressure on the ground. But,the noise pollution problem coused by subway is getting worse. Recently, a driver of the metro train complaints that the noise in the driver cab is abnormal,their physical and mental health is sffected seriously. In this paper,field test and numerical simulation are used to analysis the couse of abnormal noise in the cab of the metro train, the main work and conclusions are as follows:First, the overall level of noise in the cab of the train was investigated. The results show that when the train runs on the line with a speed of 60km/h, the noise in the cab is far more than the limited value 80dBA in most area. And when the train runs on the up-line, the noise in the cab is 2.7dBA more than that train runs on the down-line. Also, it is 5.4dBA more than the limited value.Sound source identification and spherical array test technology was used, to identify the source of the sound in this study. And the results show that, the source of the noise in the cab mainly comes from the side doors of the cab. We can speculate bassed on the vibration and sound insulation test data, that source is caused by two resons,the vibration of the axle box and the sound out of the cab comes into the cab from the area where sound insulation performance is poor. In the same way, Statistical Energy Analysis method have been used to analysis the relationship of the sound insulation and noise level in the cab. Results show that after the improvement of the sound insulation performance of the side doors, the noise in the cab have decreased by 1.7-3.5dBA.The noises-after and before the wheels re-profile -in the cab had been compared, results show that,there is a 12.5dBA difference of the noise after and before the wheels re-profile process. And the roughness of the rail was also investigated from the results we can know that, the 30-63mm corrugation is the main couse of the noise at 295Hz? 359Hz and452Hz.The relationship of the roughness of the rail/wheel and the noise in the cab was also studied,suggestions about the rail/wheel re-profile were oferred at the end of this research.In summary, the main causes of the abnormal noise in the cab are the roughness of the rail/wheel and the poor sound insulation performance of the side doors of the cab. On the one hand, the serious roughness of the rail/wheel lead to the strong vibration of the axle box,the vibration passes to the side doors, noise was produced by the vibration of the doors. On the aother hand, the serious roughness of the rail/wheel lead to the strong rail/wheel noise,the noise comes into the cab through the part whose sound insulation performance is poor. In addition, the speed of the train? the decay rate of the rail and the type of the tunnel are also influence the noise in the cab in some extent.