Seal gaps around doors, windows, vents, and outlets with acoustic caulk or weatherstripping
Install a solid-core door
Add a door sweep and perimeter seals
Use thick curtains or acoustic drapes over windows
Add rugs, carpets, and underlayment on hard floors
Hang acoustic panels on walls and ceiling
Add bass traps in corners
Increase wall mass with extra drywall or mass-loaded vinyl
Decouple walls or ceilings with resilient channels or sound isolation clips
Fill wall cavities with mineral wool or fiberglass insulation
Use double-pane or laminated windows
Build a room-within-a-room if maximum isolation is needed
Reduce vibration transfer through furniture and equipment with isolation pads
Cover large reflective surfaces with soft furnishings
Keep speakers, appliances, and noisy devices away from shared walls
Use white noise or sound masking if complete isolation is not possible