To reduce sound, you must create a barrier between the sound and the ear that captures the sound. Homes do that with walls, roofs and windows that block sound waves from entering. To increase a window's ability to block sound and increase its STC rating, the window manufacturer must: Add mass (make glass thicker) Add air space (increase the distance between window panes) Use laminated glass, a glass-plastic-glass sandwich that further reduces noise transmission CitiQuiet windows are inserts installed behind your existing window, which adds up to 4 inches of dead, sound-reducing air between the principal window and the new interior window. The company's 1/2-inch laminated insert has a STC rating of 38 and promises up to a 95% noise reduction depending on the size of the window opening, apartment location, and type of noise. Zeluck Inc. manufacturers high-end, dual-pane windows that a 1-1/4-inch thick and reach an STC rating of 42.
