Pressure Waves Radiated Directly from Tunnel Portals at Train Entry or Exit

抄録

It is well known that when a compression wave generated by a high-speed train entering a tunnel propagates through the tunnel and arrives at the far exit, a "micro-pressure wave" is radiated from the exit portal toward the surrounding area. In addition, the entering train generates impulsive pressure waves outside the tunnel, which are radiated directly from the entrance toward the neighboring area. A similar phenomenon also occurs when the train leaves the tunnel. We call the former a "tunnel entry wave", and the latter a "tunnel exit wave". Although the tunnel entry/exit wave is usually weaker than the micro-pressure wave, they could cause an environmental problem with increases in the train speed. In this paper, fundamental characteristics of the tunnel entry/exit wave are described based on the results of field measurement, model experiments and simple acoustic analysis.