For frequencies above 200 Hz, the measured TL for 18 mm glass is far below the performance predicted by mass law. Because of this effect, the STC rating for single glazing increases very little with increasing glass thickness. Laminated glass may closely approach mass law performance above the coincidence frequency. It should be noted, however, that damping is normally temperature dependent. At typical Canadian winter temperatures, the increase in TL due to glass lamination may be drastically reduced.
Typical plastics provide noise reduction similar to that for glass of the same mass.
For example, the TL for 8 mm thick plastic resembles that shown in Figure 1 for 4 mm glass, which has approximately the same weight. The TL of double glazing is strongly dependent on the features of the cavity between the two layers of glass. For each doubling of the air space, the STC increases by approximately 3. The STC also increases with increasing glass thickness. 6-8 Figure 2.