Functional Relationships between Sound Powers Radiated from Noise Sources of High-Speed Train and Its Speed

To solve the problem that the existing logarithm empirical formula cannot satisfactorily fit the relationship between the sources contribution rate and the speed, the microphone array was used to identify the external sound sources of a high-speed train at different speeds. Dividing the train surface into sub-regions with the location of the known main noise sources, the relationship between sound power level and its contribution rate of main noise sources sub-region and train speed were analyzed quantitatively. Then, according to the characteristic of different kinds of noise sound powers increment rate with speed, the new fitting formula was established based on the existing logarithm empirical formula. Finally, the new formula was verified on the noise data of different train. The results show that when the train runs at 350 km/h, radiated noise from the lower region of railway system dominate the total radiated noise, which account for more than 70%. The sound power of the rising pantograph region is significant in the local region as well, which account for more than 50%. With the speed increase, the contribution rate of lower region decrease and the pantograph regions increase, and each regions change rapidly first and then slowly, finally become stable. Using the advanced fitting method, the fitting degrees of sound power level and sound power contribution rate with speed in the source regions of the train are all above 0.9.