Sound Proofing Wall - Insulation density

[neal1980]

Hi,

I know this comes up alot but after some advice on insulation. I am renovating my house and although my neighbors are a joy i'm future proofing whilst I have the chance with extra sound proofing.

So far I have ripped the ceiling down, first put 10mm sound deadening foam then 100mm 70kg/m3 Insulation then 2 layers of 12.5 Sound Shield Plasterboard.

Now onto the dividing wall I have firstly glued 10mm sound deadening foam, then fixed battens every 600, going to lay 75mm of insulation then 2 layers of Sound Shield 12.5 or 15mm.

I thought from my re-search that the higher kg/m3 the better for sound proofing so I was looking at some Knauf RS140 140mg/m3 but I have found a site that says its a balance and too higher density can be too rigid and make the problem worse. Lots of people using the Rockwool RW45 (45 kg/m3)....but as this is a once off opportunity I dont mind the denser stuff if it will help more.

Can anyone offer and advice, I have the choice of any insulation at the moment 75mm thick.

Neal