How to Soundproof Windows
The Soundproofing Website

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SUPER Soundproofing Plugs for Windows

Windows are one of the most common entries of noise into or out of a room. Glass and wood window frames seem to be invisible to sound.

An alternative to replacing the window with double pane glass (a noise reduction of about 20%) or vinyl frames (noise reduction of about 30-50%), is to make a removable "plug" to block the sound coming through the window. While this will also block light, it won't matter if the window is a bedroom and noise is keeping you from sleeping. If light is wanted for day use, make the plug removable. It can then be removed to allow light to enter the room.

Measure your window frame to see how much depth there is to the sill. This will be the thickness of your plug. If there is 3" of the sill, the you would use 3" boards. Glue, nail or screw a box frame together to fit inside your window opening. 1/2" pine from the lumberyard is fine. You can use thin boards, but 1/4" plywood works better to make a covering for the box you've made. Line the inside of the box with "Super Sound Proofing mat'. You can use whatever thickness you like, but the more the better. You can make 3" thickness from layers of 1/2" mat. You can attach the mat inside your frame with contact cement or with staples or nails. If you have a very deep window frame and you don't want to fill the box you've made with soundproofing mat completely, use a block of Styrofoam, then put the mat over it. You can get Styrofoam from arts and crafts stores or better yet because it's free, from packing boxes! Yep, the white stuff. You could also use bagged Styrofoam "peanuts"... but don't omit the soundproofing mat.

The plug should fit the window opening very securely without cracks which will allow sound to enter. It probably won't matter which way it is inserted, but if you place the soundproofing side out and the plywood side in, you could add another layer of soundproofing mat to the room side. Make sure it's cut an inch or two oversize to help block the sound that may come through the edges of the plug and the window frame.

To make the plug easy to handle, if you intend to remove it, attach some cabinet handles to it so you can grip it well. It will be lightweight enough for a woman to handle if you use thin boards and plywood and the window frame isn't very large. An added bonus of such a soundproofing plug is the thermal insulation property of the window goes way up, keeping you warmer in winter and cooler in summer! A 1" layer of our Super Sound Proofing Mat" is about R-5.5 so it wouldn't take too many layers to equal a very high "R" number. (The R number refers to the insulation quality of a material).

If large amounts of sound are being passed by a window, either way, more drastic measures may be needed. This could entail lining your plug with a limpid material to give it more mass. Asphalt roofing tiles can be stapled inside your box to do this, but will add considerably to the weight. If a plug as described accomplishes the purpose, it may make sense to leave it in place rather than to make it removable. In that case it can be sealed by caulking it around the edges, which will help the soundproofing job.

You can dispense with fabricating a plug frame if your windows aren't very large. We also have the mat in 1 1/2" and 2" thicknesses, which are firm enough to push into place in the window frame. A dab of cement like household "Goop" will hold the mat in place, if needed. If you intend to leave it in place, caulk around the edges.

You might also consider a shutter for the outside of the window if it's practical. 5/8" plexiglas will work, but must fit well!

Remember, at least a 6" dead air spacing between glass is needed for meaningful reduction of sound in a double framed window.

We would like to thank The Soundproofing Website for the above information. Please visit their website at This site offers the Super Soundproofing Mat as well as other materials for noise control. Clear, practical information and free advice about using common materials for soundproofing can be found here.

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