Soundproof a door that is not in use

Hi guys We have a door which we do not use anymore (leads to another office) which we would like to sound proof as much as possible. The depth available between the door and the edge of the wall is about 11cm. I thought about stuffing high density rockwool (2-3" thick) all over the opening, than add 2 layers of "acoustic" drywall with tecsound between them. Wll adding a third layer of drywall with another layer of tecsound help? Any other suggestions? Should I seal the gaps between the door and the existing wall somehow before doing this? Any help would be highly appreciated!

Hello & howdo'? Without a little more info, this is a bit of a "how long is a bit of string" question. What amount of insulation do you need and what is the density of both your door and the wall around it? Have you seen Greg's transmission loss calculator? Best wishes, John. https://docs.google.com/spreadsheets/d/1IVsp3j7zNmLHkQVeUgBhFuN_cohSrlkj5RNrM6SXGpA/edit#gid=1543869474

If you will never ever use the door again then I would screw the door shut into the framing, then seal all the gaps around the perimeter with caulk. squeeze it in and go to town, it doesn't need to look pretty. Then depending on how seamless it needs to look I would either build some framing in the door way, fill the cavity with cheap, low density insulation, then attach the drywall layers to the framing, or attach it to the surrounding wall so that it overlaps. Then seal all the edges with caulk. How many drywall layers you use depends on the construction of your surrounding walls? You would ideally match the surface density of those walls, or increase it. How about the other side of the door? Is it boarded up already? If not then add drywall to that side of the door but do not leave a gap, just apply it directly to the door and seal it all up. Paul