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Advertising supplement provided Solutia Inc. and Arch Aluminum & Glass Co.

Sound transmission of a material is largely dependent on its mass, damping and stiffness, although in some cases size, temperature and edge anchoring can also alter the test data. Increasing glass thickness, and thereby increasing its mass, is one way to improve sound isolation performance.

Augmenting glass stiffness or adding an insulating air layer between two plies of glass are other ways of improving sound insulation performance. The use of two lites of glass is generally effective only for an air space thickness larger than 0.5 inch (12.7 mm).

The remaining variable for improving sound transmission performance is glass damping. Damping is a mechanical property of a material or system, which quantifies the rate of dissipation of vibrancy energy into heat energy. For example, a bell has a low damping, and when a bell is struck, vibration persists or rings, resulting in sound that correspondingly persists. However, the ringing or vibration persistence can stop by holding the bell with one hand. This is a form of damping.

Generally glass has very low inherent damping and is usually only sufficient in reducing sound transmission loss within certain frequency ranges. By using laminated glass made with a polyvinyl butyral (PVB) interlayer, glass damping will increase and result in significant increase in STL. The damping increases attributed to glass through the use of a PVB interlayer could otherwise only be obtained through significant increases in glass thickness or increases in air spaces for insulating units. When laminated glass with a PVB interlayer is used in air spaced or insulting glass configurations, the benefits of damping are even greater.

Acoustical glazing

Isolating interior building spaces from exterior sound is important if those spaces are to fulfill their intended purposes. An interior space that allows too much noise to be transmitted from outside may result in poor or inadequate conditions.

For example, a hotel located near a train station that has windows that do not sufficiently limit the amount of train noise in the guest rooms may fail to provide what hotel guests are looking for: a good night’s sleep. Hotels are an obvious example; however most types of buildings (schools, office buildings, condominiums, etc.), and the people inside those buildings, can be adversely affected by high levels of environmental sound transmitted from outside.

When usual glazing configurations are not sufficient to limit the transmission of sound into building spaces, glazing configurations with enhanced sound transmission losses or acoustical glazing must be considered. There is no single definition for acoustical glazing, but most use a combination of a polyvinyl butyral (PVB) interlayer and an air space between multiple lites of glass.

Laminated glass made with a PVB interlayer is a highly effective way to reduce unwanted sound transmission even when used in a standard window design. It has been proven as a highly viable solution to the complex problem of retaining the integrity of a building’s architectural design while simultaneously providing the most practical, effective form of sound control available in glazing systems.