Passengers' demands for riding comfort have been getting higher and higher as the high-speed railway develops. Scientific methods to analyze the interior noise of the high-speed train are needed and the operational transfer path analysis (OTPA) method provides a theoretical basis and guidance for the noise control of the train and overcomes the shortcomings of the traditional method, which has high test efficiency and can be carried out during the working state of the targeted machine. The OTPA model is established from the aspects of "path reference point-target point" and "sound source reference point-target point". As for the mechanism of the noise transmission path, an assumption is made that the direct sound propagation is ignored, and the symmetric sound source and the symmetric path are merged. Using the operational test data and the OTPA method, combined with the results of spherical array sound source identification, the path contribution and sound source contribution of the interior noise are analyzed, respectively, from aspects of the total value and spectrum. The results show that the OTPA conforms to the calculation results of the spherical array sound source identification. At low speed, the contribution of the floor path and the contribution of the bogie sources are dominant. When the speed is greater than 300 km/h, the contribution of the roof path is dominant. Moreover, for the carriage with a pantograph, the lifted pantograph is an obvious source. The noise from the exterior sources of the train transfer into the interior mainly through the form of structural excitation, and the contribution of air excitation is non-significant. Certain analyses of train parts provide guides for the interior noise control.
Track construction is likely to exert a significant effect on railway environmental noise. In this study, a detailed comparative investigation was conducted to analyze the differences in the external noises generated by a Chinese high-speed train passing through typical lines at different speeds. Acoustic experiments were conducted on both viaduct and embankment sections by using a microphone array having 78 channels, to distinguish the effects of two types of track structures on the sound fields around these, identify the sources, and determine the contribution and distribution of each part of the train. The quantized sound power contribution of each region on the train surface determined using the identification results obtained from the experiments and analysis shows that the main noise sources of the train are located in three regions: the lower parts, bogie, and train body. The pantograph was the dominant noise source at speeds above 300 km/h. Considering the embankment as a reflective surface compared with the viaduct, the ground reflection effect results in a higher sound power level in the embankment section. Furthermore, the largest difference between the two sections increases to 1.8 dB at a speed of 350 km/h. In addition, the reflection effect is more apparent at high speeds, and the reflection is evident in the low-frequency band (<1000 Hz). The analysis of the experimental results is effective for identifying the difference and satisfies the requirement for reducing external pass-by noise in typical operational lines.
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