Sound proof my guest unit carved out of main house
Sound proofing is difficult.
One extra layer of drywall and green glue will have a noticeable effect but don't expect it to be dramatic.
To give you an idea.  I have a laminate with underpad, 2&quot; concrete floor, 2x10 floor assembly, roxul batt insulation, 5/8&quot; drywall between me and people living under me.  This deadens noise such that I can't understand conversations - I can hear them they sound as if someone might be outside walking by having a conversation.
It would help if you drew a plan view of how your guest room is craved out.  The best solution for this would be to build a extra wall off set from the existing one that separates the spaces, fill the wall with roxul insulation (you want mass), and drywall it.  Depends if you can stand to loose 4.5&quot; of your room.