3DInvestigation of the pressure waves generated when a train passes by an over-bridge
  • Investigation of the characteristics and mechanism of the pressure waves generated when a train passes by an over-bridge
  • Analysis of the pressure waves by model experiment and acoustic theory
  •    As train speeds increase, low-frequency sound is becoming to cause an environmental noise problem in wayside areas. One example of the low-frequency sound in railway is the pressure waves generated when a train passes by a nearby structure, such as an over-bridge, in an open section. They are not large enough to cause serious problems for the current train speeds but can be as influential as the tunnel micro-pressure wave if the train speed is significantly increased.
       On this phenomenon, we conducted field measurement (Fig. 1), model experiment and theoretical analysis and clarified the velocity dependency, distance attenuation and the directivity of the pressure waves. The mechanism by which the pressure is generated can be explained by the combination of micro-pressure waves and entry/exit waves radiated from both sides of the structure (the over-bridge) by regarding the structure as a very short tunnel. Based on this knowledge, we developed an analytical method to predict the pressure waves for the over-bridge that is long enough to generate distinct pressure waves (Fig. 2). The predicted results were compared with the experimental ones and showed a good agreement (Fig. 3).
       These study results can be utilized for wayside environment assessment before train speeds are increased for Shinkansen or other high-speed railways.

     

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