Sound Testing |
Acoustical GlazingThe acoustical properties of glass are of considerable importance in many applications, not the least of which being exterior windows facing a busy street or highway. The ability to transmit light does not directly affect the ability of glass to block sound transmission. In fact, it is possible to construct glazing systems that are more effective in reducing sound transmission than solid concrete! However, these glazing systems are considerably more expensive than concrete. |
Acoustical DesignFor most buildings, the windows are the dominant sound transmission path for exterior noise. This is Hiring a qualified consultant to make these design decisions is the best way to ensure that you get the performance you need at minimum cost. Table 1 lists the approximate STC rating of common glazing systems.
Remember, the STC is directly proportional to noise reduction when comparing like sounds. For example, the noise level on the quiet side of an STC-30 window will be approximately 10 dB greater than it would with an STC-40 window and the same noise source.
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Table 1 Glazing STC Ratings
*perimeter lined with acoustical material |
Monolithic and Laminated Glass
You will note in Table 1 that increasing the thickness of monolithic (solid) glass increases the STC rating. However, increasing the thickness greatly increases cost, without achieving a comparable improvement in performance.
Insulating Glass
As far as double glazing is concerned, the larger the air cavity the better the STC rating. Air cavities less than 1/2" should be avoided. Note that double glazing with two layers of glass and a 1/4" air space actually, has a lower STC rating than a single layer of 1/8" glass! Air cavities larger than 1" thick are not generally available in sealed, insulated units. However,acoustically designed systems arc commercially available with air cavities as large as 8 inches. Triple glazing is not generally recommended because it is much more expensive than double glazing, and its acoustical performance at low frequencies is generally poorer than double glazing of the same total thickness.
This is why installation should always be provided by professionals experienced with acoustical glazing. |
Acoustical Performance of Glass and Wall Constructions
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