Seal all gaps, cracks, and penetrations with acoustic caulk
Add weatherstripping around doors and windows in the wall assembly
Increase wall mass with additional drywall layers
Use damping compound between drywall layers
Decouple the wall with resilient channels or sound isolation clips
Fill the wall cavity with mineral wool or fiberglass insulation
Replace hollow-core doors with solid-core doors if applicable
Add mass-loaded vinyl to the wall
Install staggered studs or double-stud framing for major upgrades
Use acoustic panels or fabric-wrapped absorbers on the room side
Seal electrical boxes with putty pads
Avoid rigid connections that bridge both sides of the wall
Extend soundproofing to adjacent weak points like ceilings, floors, and vents