Door and door frames questions

My new studio has double opening exterior doors with 15mm double glazed panels for almost all the door. I'm fitting heavy duty double rubber seals all round the sides but I would still like to consider building another set of double interior doors to improve sound attenuation. I understand that they need to have mass but my questions are as follows: How can I fit the interior door frame without connecting it (i.e. bolting or screwing) to the outside frame? In other words, how do I decouple it? How do I finish my double/triple layer plasterboard and residual channel around the door frames? Leave a gap and fill it with backer rod and mastic? Thanks Paul

tell us more about your current construction... else we would be guessing.

Its a self contained timber frame construction in a far corner of my garden. It has a slate roof. The roof has 125mm joists and the walls are 100mm timber stud. The roof is 40 degrees, double pitched. The inside ceiling is approx 4.1m long and each pitch is about 2.4M deep including an external overhang; the actual pitch span to the wall plate from the ridge board is 1.9m. The walls and ceiling will all have double layer high impact plasterboarding screwed to Resilient Bar. I intend to use Green Glue in between each layer and screw each layer to the RC1 taking care not to short circuit the Gyproc layers to the stud walling. I intend to use a vapour barrier to hold the RWA45 in place; I am installing a combo A/C unit for heat/cooling which also provides fresh air ventilation. At the corners and Gyproc joints I will use acoustic mastic. The overall dimensions are 4.2m x 3.0m and a pitched roof height of 4.0m. Walls are 2.4m high to the gables. There is a double glazed double door in the middle of the 4.0m wall. The oustide is oak featherboard clad over 25mm battens; breathable membrane, external grade 6mm ply screwed to a 100x50mm stud wall. Hope that helps?