Install an entirely independent stud frame in front off (not touching!) the existing wall. Leave a minimum of 25mm airgap between the existing wall and the new stud. The stud can be constructed from timber or metal track and stud. Use a minimum of 50mm stud, the deeper your stud and cavity created the better the performance will be at low frequency.
Install the appropriate size RWA45 Rockwool insulation between the studs. i.e if your stud is 50mm use 50mm insulation.
Fix Genie clips to the studs (see full genieclip install instructions on the product page). The genieclips are install in a diamond pattern at 1200mm centres based upon 40kg of mass per M2. Install the genie clip furring channels into the genieclips at 600mm centres.
Fix dB Siniat Acoustic Plasterboard (Blue) into the genie clip furring channels. Seal the perimeter with acoustic sealant and any gaps between the boards.
Install Tecsound SY100 to the face of the plasterboard. Cut your tecsound into manageable lengths. Installing the Tecsound is a 2 man job to get it done well first time. You can hang it vertically (like heavy wallpaper!) or horizontally starting from the bottom and working up. Butt joint the Tecsound without and overlap. Ensure the entire wall is covered and seal any gaps and perimeter with acoustic sealant.
Over board the Tecsound with Siniat Fireline (pink) plasterboard 15mm. Fix through the Tecsound and dB Siniat board to find the studs. Seal the joints and the perimeter of the room. The wall is then ready to be finished. This can be wet plastered or using tape and joint method.