@picandor @LukeAlmighty if it is then i doubt it does a good job. the sound will just roll off of them instead of getting trapped like it does with foam acoustic paneling. especially if it's just solid metal, it would likely be worse than bricks. the shape of the walls and them not being parallel is way better for acoustics.

now if we're talking about soundproofing, then metal is dense as fuck and it's good for that, but you'd think the train being underground would be enough to the point where a bunch of metal slabs aren't going to do much for that.