What is STC?
Sound Transmission Class (STC) is an integer rating of how well a building partition attenuates airborne sound. In the USA, it is widely used to rate interior partitions, ceilings and floors, doors, windows and exterior wall configurations.
STC gives you a rough idea of how much sound a wall, for example, might stop. STC is the most common sound reduction measurement in use. As common as this measurement is, it is quite limited and should not be totally relied upon for real-world soundproofing expectations.
STC is calculated by taking the Transmission Loss (TL) values tested at 16 standard fre- quencies over the range of 125 Hz to 4000 Hz and plotted on a graph. Your curve (what you actually measured) is compared to standard STC reference curves (see appendix). If your wall graph is closest to a standard STC 35 curve, your unit is said to have an STC rating of 35.
OITC is a newer rating system developed specifically for measuring sound transmission of low- and mid-frequency noises through exterior walls.
While not as well known as STC, OITC is a more appropriate measure when comparing the true sound control performance of a window.
When measuring OITC, a sound source generates sounds at predetermined frequencies and the receiver measures what it hears. These frequencies have a wider range, 80 Hz to 4000 Hz, in order to account for lower-level noises often heard outdoors, such as traffic and airplanes.
Similar with NFRC rating, the STC and OITC rating are highly determined by the IG packaged used for that specific unit.
|Glass 1||Spacer||Glass 2||Total||STC||OITC|
|Glass 1||Spacer||Glass 2||STC||OITC|
|9.9 lami||19.1||9.9 lami||42||35|