What are the differences between STC & Rw ratings?
Both are laboratory test results and directly equivalent, however: STC = Sound transmission class that was originally intended for measuring internal sound transmission such as the human voice (high frequency). Rw = Weighted sound reduction index that uses airborne sound and is viewed as being more appropriate for rating the attenuation of external low frequency noise, such as traffic. This means that a product may have a 30 STC but be closer to 25 dB in noise.
