When it comes to sound, sound control is essential to living a happy, healthy life. People expect a certain level of privacy and silence, especially in their homes. Therefore, in recent years sound control standards have become a part of building codes. Part of an overall sound control strategy is to choose doors that absorb and block noise, rather than transmit it.
Sound rating systems are critical for optimal building design and product specification. Two of the most common sound rating systems are Sound Transmission Class (STC) and Outdoor-indoor Transmission Class (OITC).
It is the most common rating used in North America for determining airborne sound transmission loss between 125 and 4,000 Hz. This range covers the majority of common noises we hear including speech, television, music, dogs barking, and other similar annoyances. A high STC rating often shows improved performance. However, the rating is essentially an average over the 16 frequency points tested.
Testing covers a wide range from 80 Hz to 4000 Hz. This wider range, and in particular the lower frequency levels of the OITC testing, captures lower frequency sounds such as road noise. So if you live on a busy street or near an interstate highway, you will want to consider the OITC rating.