Soundproofing of internal stud walls

[HomerSimpson]

I have built stud walls upstairs in our new extension using 89mm CLS and plan to clad them in 12.5mm plasterboard plus a skim.

To meet Part E for soundproofing (and thermal) I was just going to fill them using the standard 100mm Crown wool on a roll. I then started to research all the 'acoustic' products made by Isowool, Knauf etc and have now got thoroughly confused? Can anyone advise me on what's the best way to meet the 40dB regs?

Would the more solid 'slabs' be better than the rolls as they seem to be more dense? Or is standard 100mm loft insulation good enough?

 

[Deluks]

The difference between either of these materials is minimal, use whatever is cheapest/readily available. Whatever you go with, make sure the cavity is completely filled with insulation for best results.
For better soundproofing use 2 layers of 12.5mm plasterboard. This will be more effective than any type of insulation alone with a single layer, and is relatively cheap.