A quote from the article:
The nose of the E5 Series, at 15 metres, is a massive 9 metres longer than the previous incarnation of the bullet train (shinkansen), the E2 Series. This, according to its designers at JR East, will help eliminate the phenomena of “tunnel boom”.
Japan’s rail tunnels are somewhat narrower than their European counterparts, so when the shinkansen enters a tunnel at speeds above 200 kilometres per hour, the sudden increase in air pressure can cause a loud “boom” at the other end of the tunnel. In some cases, such shock waves are thought to have damaged tunnels in Japan, ripping chunks of material from tunnel ceilings.
Nothing more than a high speed piston (train) entering a cylinder and compressing the contents of that cylinder. If you have a mile long or so tunnel that is a lot of air to get moving and push out the far end of the tunnel. The article makes no mention of what happens when there is a double track tunnel with trains entering from both directions at relatively the same point in time.
When a train of the new design enters a tunnel at 150 plus mph, and looking at the shape of it…I wonder if that “loads up” the front suspension / trucks. Looks like the wedge design would force the train body down heavily loaded on those trucks.
One might wonder if the pressure continues to build as it compresses the the atmosphere ahead of it thru the tunnel. Judging from the comment in the article of smaller clearances between trains / tunnel bore. Or did it simply say smaller tunnel bores…with smaller sized train bodies as well.
As a GI decades ago…we rode on Japanese trains and we were warned of tight clearances when we got on so as not to stick arms, etc…outside the window.
It’d be an interesting experience to be near the far end of a tunnel and just hear this huge BOOM come out of the empty bore. I wonder if one could feel the rush of air way ahead of the train.