Urgent - Insulation between stud wall

[Jakeee]

I'm about to buy insulation for stud walls, between 2 bedrooms and a landing area. What is best for sound dampening between 4x2 wood (90mm)? I have the follow options in my local builders merchant for tomorrow's delivery: Earthwool Acoustic Roll (50mm), Knauf FlexiSlab (90mm) or normal rockwool type (100mm)?

Not sure if I should get the 50mm roll and leave a gap or stuff it full?

 

[Jakeee]

If you're putting up a fresh stud, put acoustic cladding on the exterior, it will help to stop sound waves from starting vibration in the wall rather than trying to put stuff in the wall to deaden the sound (which will work, but generally isn't as effective).

These are internal walls which are going to be plastered, need to make best of the situation? I have 4X2 Wood, 12.5mm plasterboard, any recommendations on the internal insulation?

And what do you recommend for acoustic cladding?