Install double-pane or triple-pane windows
Use laminated glass
Add window inserts
Seal gaps with acoustic caulk
Replace worn weatherstripping
Install heavier curtains or acoustic curtains
Add exterior storm windows
Use soundproof window film
Fill window frame gaps with backer rod and sealant
Upgrade to airtight window frames
Add interior shutters
Use removable window plugs
Close and lock windows tightly
Add insulation around the window frame
Reduce vibration with proper mounting and sealing