b"There are two classifications for noise control by comparing Sound Transmission using either STC(Sound Transmission Class) or OITC (the Outside Inside Transmission Class). STC rating is the result of the measurement of 16 frequencies after passingthrough a barrier while OITC measures the attenua-tion ability of a barrier but more weighted to thelower frequencies associated with traffic, aircraft andother transportation caused noise. STC numbers areusually higher than OITC, and the differencesbetween them tend to stay reasonably constant.The key to blocking sound transmission through a It is even desirable to use neoprene, cork (or otherwindow is breaking up the sound waves, and manu- similarly performing material) sill shims to rest win-facturers employ a variety of technologies to achieve dows on which will significantly contribute to thethat goal. dampening effects the use of other sound mitigationStandard impact-resistant laminated glass reducesmaterials will afford. noise because the (PVB) interlayer has a differentThe key is to isolate the window or door unit in the density from the glass, breaking up the sound. Acavity, sort of suspend it, while doing everything standard insulated window with one layer of laminat- possible to fully integrate the window or door into theed glass would have an STC of around 32 to 35, a sig- water management system of the wall.nificant improvement from a standard insulated win-dow with an STC of about 29 or less. Finally, the frame material of the window or door canbe a major influence on the sound transmissionAdding a storm panel or an additional monolithic properties. Composite, wood or uPVC windows arepane to the window can push STC ratings to 39 or best because they have less vibration tendencies thathigher. Sound needs air to move, so the 1/2inches metal window products. to 3 inches of dead air space between the primaryand secondary window causes the noise to die.Asymmetrical Glazing(panes of glass of differentthickness in one multi-pane unit) is a anotherapproach to reduce soundtransmission often at alower cost than laminatedglass or storm panels,because as the sound wavetravels through the differ-ent types of materials, it'sbroken into different fre-quencies which has the effect to dissipate the noiseachieving STC ratings of 30 to 34 without laminate,and with a price premium as little as 3 percent to 20percent. The technique also can be combined withother technologies to further improve the window'ssound abatement. The best performing sound-control GLAZING UNITRATINGSwindows incorporate a combination of glass thick- CONFIGURATION OITC STCness, multiple units and lamination.Monolithic (1/4) 29 31Installation Laminated (5/8) 36 40Because the goal of Sound Control Windows and Dual Pane IG (1/4-1/2-1/4) 28 35Doors is to both block and breakup the path of the Gas-Filled 1 IG 24 35sound through the window or door unit, it is especial- Triple Pane (1/4-1/2-1/4-1/2-1/4) 31 39ly important to use noise abatement materials to sur-round the window in the cavity (dense foam is the Suspended Film IG 23 30best), and prevent as much vibration transfer Asymmetrical IG (3/16-9/16-1/8) 25 30between the wall and the window (utilize neoprene Standard Wall (5/8 Gypsum 2x4 16OC) - 39sound isolation shimming, for example). Block Masonry Wall (4-8 Hollow) STC 41-51Window Fitters Guide to Window Installation1392020 AWDI, LLC Do not reproduce without permission"