Any glazing fitted in a frame provides sound insulation. However, some types of glazing such as laminated glazing with resin or acoustic PVB, together with some specific types of double-glazing significantly improve acoustical performance. Single-pane 8 mm glazing acts as a simple partition providing insulation levels of approximately 32 dB, with a critical drop in sound reduction index between 1000 and 2000 Hz. Single glazing of an identical thickness but including an acoustic PVB interlayer will reduce this critical drop significantly, resulting in a 37 dB Rw.
The acoustic effect of double-glazing, however, is somewhat more complicated, necessitating a greater understanding of not only the pane and PVB interlayer but also the unit configuration, width of cavity and type of noble gas used for thermal performance. As a rule, sound insulation can be improved by about 3 – 5 dB, with the best results achieved by maintaining a PVB interlayer. However, the cavity contributes to the drop in sound reduction index between 1000 and 2000 Hz because the noble gas infill transmits vibrations from one pane to another, unless the panes are asymmetrical.
Glazing acoustic performance is influenced by a combination of diverse and complicated factors driven by weight, stiffness, configuration and cavity specifications in a non-linear fashion. Therefore, acoustic specialists are often required to provide further insight into detailed design and construction practice. The true effect of sound reduction indexes cannot be determined through calculation alone, but instead through physical testing.