The Difference between CAC and STC

Sound Blocking (Soundproofing) and Sound Absorption: What's the Difference

Sound is like water. It doesn't have a shape or form, but molds itself to its surroundings. And like water, sound can be absorbed by some materials and contained by others. Click here to learn more sound basics.

Sound absorption products soak up sound. They absorb sound waves and prevent them from bouncing off the walls. They improve the quality of the sound within a room. Click here to learn more sound absorption basics.

Soundproofing products, on the other hand, trap the sound. They contain the sound within a space, making it impossible for the sound to move to other parts of the building. They also stop unwanted sound from entering the room. Click here to learn more soundproofing basics.

What's STC?

To be able to compare the performance of different soundproofing products, we rate them by how much sound they can block. This rating is called STC, which stands for Sound Transmission Class. Click here to learn more about STC.

The higher the STC rating, the better the material is at blocking sound.

What's CAC?

Ceiling Attenuation Class (CAC) is used to determine how well ceiling tile soundproofing products block sound. Essentially, it's the STC of ceiling tiles.

CAC measures how much the sound pressure level changes between two rooms connected by a ceiling. It's measured in decibels, so a ceiling that blocks 21dB of sound will have a CAC of 21.