Does it drown it out completely? I'm the princess and the pea.
That I don't know. But you are comparing apples and oranges. With slate roofs, you have a loft and insulation. If you had a polystyrene roof, you wouldn't need the loft.
But if you had a polystyrene roof, and a loft, then it would probably be better.
I wonder if things are done differently here? Metal roofs are not seen often, but the few I have experienced were loud. People talk about how they love the noise! In the past, the layer of insulation required was actually very thin, and now it is much thicker (we had it replaced for this home, and it was updated to fit with minimum current requirements). Maybe that has something to do with it? I really wouldn't know.
Are lofts common there? I mostly see attics here with few converted into usable space.