Special edition paper

When a train enters a tunnel at high speed, sometimes an explosive sound occurs at the exit of the tunnel, shaking windows and doors of houses in the vicinity. That phenomenon is caused by a tunnel micro pressure wave (hereafter “micro pressure wave”), the mechanism of which is shown in Fig. 1. First, a high speed-train entering a tunnel generates a compression wave at the entrance of the tunnel. That compression wave propagates through the tunnel while deforming. When the compression wave reaches the exit of the tunnel, a part of the wave is emitted as a pulsing pressure wave. That pulsing pressure wave is a micro pressure wave. Countermeasures for micro pressure waves is one of the most important issues in achieving further speed increases of high-speed trains. Optimizing the nose shape of the train brings about some effects of reduction of micro pressure waves, but such optimization is limited if we are to maintain the functions of a train. Accordingly