A window plug treatment as a noise-reduction solution can just as effectively soundproof your home, the way a second interior window can---and without drilling a hole in your pocket. Design your own plugs from available soundproofing materials or have them custom-built. But because window plugs also block off ambient light, you may want to make your plugs removable, so you can enjoy ambient light any day you like.
Measure your window frame with the tape measure and determine the frame's depth to the sill. This measurement will determine the thickness of your soundproof foam.
Line your window with aluminium foil to create a heat reflector, particularly if that window is fully exposed to outside heat. The reflector will protect your window glass from too much heat, when the soundproofing mat is installed.
Cut out the fibrous board to the same size as the soundproof mat. Make sure the mat board is large enough to cover your window's interior frame up to its outermost edges. The soundproof mat should be at least 1 inch oversized, to fit tightly into your window frame and achieve maximum noise reduction.
Cut a few finger holes in the mat board, to make plug removal easier when you want some light in your room.
Glue the soundproof mat onto the mat board with contact cement or duct tape.
Fit the plug into your window, making sure that all gaps are tightly covered.
To increase noise reduction in the room, add another soundproof mat on the backside of your mat board. You can also use medium-density fiberboard for your mat board, but this is heavier than other fibrous boards. Soundproof plugs have built-in insulation than can help keep your room warm in the winter and cooler in hot weather. Your soundproofing mat will not overheat, as it can withstand heat of more than 90 degrees Celsius.
Don't use wood or particle board for your mat board. They are poor noise insulators.