The Learning Center Sound performance is measured by STC (Sound Transmission Class) or OITC (Outdoor-Indoor Transmission Class). The higher the number, the better the window is at reducing sound. Stopping unwanted sound through window glass is determined by three things – mass, stiffness, and damping. Increasing the mass of any object will have an effect on sound transmission. Increasing the mass of a window by making the glass thicker will increase sound attenuation. This is why double strength glass will not transfer as much noise as single strength glass. It really isn’t possible to increase the stiffness of glass. By itself, glass has very little damping ability, but when putting a layer of a more viscous material between two pieces of glass, we make a glass sandwich that substantially increases the unit’s ability to dampen sound – thus the advantage of laminated glass. Laminated glass has an inner PVB layer of plastic that stops vibrations. If reducing noise levels is really important to you, it is best to go with laminated glass in an insulating glass unit. Laminated glass is highly effective in reducing noise, thus improving STC and OITC ratings. It's produced by permanently bonding two pieces of glass together with a tough plastic interlayer between them. It also blocks 99.5% of the sun's ultraviolet rays, helping to prevent furniture from fading. However, laminated glass can add considerable cost to a window unit.   14. What is sound reduction through glass? < back to list of questions about glass WINDOW GLASS 3245 Miracle Drive Murrysville, PA 15668 724-387-2991 PA Contractor ID PA001856