Abstract
A pressure wave is generated ahead of a high-speed train, while entering a tunnel. This pressure wave propagates to the tunnel exit and spouts as a micro pressure wave, which causes an exploding sound. From the fact that the ballast track tunnel has smaller noise than the slab track tunnel, we have suggested a new inner tunnel model to decrease the noise of the micro pressure wave, using the ballast effect. An experimental investigation is carried out to clarify the attenuation and distortion of propagating compression wave over porous plate wall in a tube
