"thorough room re-construction" Yup, was thinking I might have to do this. My building was converted into flats about 1984 and there was no real requirements for sound proofing like now. Anyway, the building is about from about 1860, so there is a little sagging of the joists and the floor boards aren't tongue and groove. The last owners put down a thick felt as sound proofing and minor surface levelling before installing locking laminate flooring.
The sound insulation doesn't work; I've since found the felt isn't butted hard up against the wall (there is a gap), and they made no attempt to screw the floor boards down and seal the gaps between. Yup they left a perfect space for sound leakage. Installation is pretty poor. I think a pissed monkey with a chainsaw couldn't have done worse :- )
I'm thinking lift the laminate, screwing down the floorboards, seal the gap between the floorboards, and fit a proper sound barrier designed to fit under carpet, then fit carpet. But what "sound barrier", how well do they work. I've got the feeling a fully floating floor is the way to go.
I've got a penny pinching plan that may work. Thinking I might sort the floor boards as described above, then fitting the felt properly so it runs to the wall then slightly up it with no gaps. I'd then fit the laminate butting up to the felt rather than the hard surface of the wall. Pretty much creating a fully floating floor using the existing laminate instead of plywood. By the way, the felt is supposed to drop 26db if installed properly. I thought that and a good carpet and underlay could be pretty good.
... just pondering really. Then I'd get a nice fat sub, but for now I can't
Felt will do virtually nothing to soundproof. The only real effective way to soundproof is through the use of sufloors, subwalls, and ceilings. Not only that, but you MUST use the correct grade of materials.
There is really a lot more that goes into soundproofing a room. You might want to google "Theater soundproofing" because there are volumes written on the subject.
Good luck.....
PS.... Once you've treated the leakage of sound so your neighbors wont hate you, be sure not to forget to treat the sound INSIDE your room with acoustic treatments(not to be mistaken for soundproofing because they're two totally different things). You'll never get clear accurate sound within the room until you've fixed the room acoustics
