Two roof problem

My potential control room is on the top floor of a building with a flat roof. To combat drainage problems, the old owner (builder) added a new roof about 1' - 2' above the old one (without removing the old one). I would like to take out the old roof from below to gain some ceiling height but I have been informed that it may be unwise as it is almost certainly tying the walls together!! So I now have two leaves of mass and an air gap (with no insulation I believe). Both roofs are of fairly standard UK construction - 9.5" joists, boarded and asphalted. I have removed the plasterboard so now I'm looking up at the joists of the old roof. It may be possible to remove most of the old roof, leaving the occasional structural joist in place, or else I was planning to put a couple of layers of plasterboard between all the old joists to add some mass but I'm wondering what the best way to fill the remaining joist depth would be. The room is low (wood floor to bottom of joists about 7'10") so I presume some type of absorption with a cloth front? I'm concerned about the fact that it's parallel to the floor but I know I shouldn't add another leaf of mass. Room will have side walls splayed out in the middle - narrowest point about 14' widening to 17'. BTW, the ceiling is not shared with any other room so decoupling is not such a problem. Any ideas would be most welcome. Thanks, Chris.

Maybe this is a really lame idea, but have you thought about leaving the old roof joists and just removing the actual roof above it? You'd obviously have to do something aesthetically with the joists going across your room, but at least you'd have that extra space above them to improve the sound.

It's not necessarily a "lame idea," but there may be some structural qualities of the roof besides the joists. You're in the right place for advice on acoustics and soundproofing, but what you probably need is a structural engineer who can work with you to ensure that nothing caves in and kills anyone. (And that's no joke!)

Thanks guys, I actually have a structural survey scheduled for Tuesday so I should be a little wiser after that happens. I am very happy to have a few joists on show but I was concerned as to whether this would be acoustically acceptable and also, if the surveyor says I should leave the entire roof in place, what would be the best way of treating it? Maybe I should report back after the survey when at least I will have a more clear view of what can and can't be done. Cheers, Chris.