If you've built a soundproof recording studio or music room in your home, you'll want to make sure the window that looks in on it is soundproof as well. Specialty acoustical windows are designed with soundproofing in mind to make them effective noise reducers, but they tend to be very expensive. You can build your own affordable, effective soundproof window from plexiglass by keeping the same principles in mind.
Walls provide better soundproofing than windows, and larger windows let in more sound than smaller ones. Limit the size of your windows to reduce potential sound transmission.
The thicker the mass of the soundproofing barrier, the greater the noise reduction it provides. Acoustical windows are made from two panes of thick, specialty glass. Build your window with two panels of plexiglass that are at least 3/8- to 1/2-inch in thickness.
Sound travels through solids better than it travels through air. Because of this, acoustical windows are constructed with at least 2 inches of dead air between the panes. While 2 inches is good, 4 is ideal. This means that the window box you purchase or build must be between 2 and 4 inches wide, with the plexiglass mounted on either side of it.
Building the Box
Measure the opening of the window. Build the box from 1-inch-thick boards that are 2 to 4 inches wide to accommodate the needed dead air space. Cut the top and bottom pieces to the same size as your opening and cut the sides 2 inches shorter than the height of the opening. Screw the pieces together with simple butt joints, with the top and bottom pieces butted over the sides. Install the box in the opening with screws then mount a sheet of plexiglass to both sides.
Improper installation of even the best acoustical window will reduce its soundproofing ability. A tight fit is crucial for maximum soundproofing because, if air can leak through, so can sound. Caulk every gap around each window to seal it closed.