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Title: China Solves 'Tunnel Boom' Problem With Maglev Trains

Link: https://tech.slashdot.org/story/25/08/08/0045...

Ancient Slashdot reader Epeeist shares a report from The Guardian: The newest
version of the maglev train is capable of traveling at 600km/h (about
370mph). However, the train's engineers have wrestled with the problem of the
shock waves which occur as the train exits the mouth of a tunnel. When a high-
speed train enters an enclosed space such as a tunnel, air in front is
compressed, like in a piston. The resulting fluctuations in air pressure
coalesce at the tunnel mouth, generating low-frequency shock waves. These are
colloquially known as a "tunnel boom" -- a related, albeit different
phenomenon to the "sonic boom" heard as aircraft pass the speed of sound.
Tunnel booms pose serious challenges to operational safety, as the shock
waves can disturb humans and animals nearby, as well as causing structural
damage. Now, however, researchers have discovered that placing innovative
soundproofing buffers at tunnel mouths can reduce shock waves by up to 96%.
This promises improvements in operational safety, noise pollution and
passenger comfort, as well as safeguarding animals in the vicinity of future
lines. [...] The porous structure of the new 100-meter long buffers, combined
with porous coatings on the tunnel body, allow the trapped air to escape
before the train reaches the tunnel mouth, suppressing the boom in the same
way as a silencer fitted to a firearm.

Read more of this story at Slashdot.

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