We wrote an article outlining STC rating if you want to dig in. If you’re using a high STC ceiling system, your wall construction needs to have a minimum STC of 40.

Imagine attaching a V8 engine to a tricycle, it wouldn’t be very effective. Note that a high STC ceiling can’t do all the work on its own, the walls and other construction also need to be rated highly. A ceiling system with a STC less than 25 is considered poor, while a STC of 50 or greater is considered high performance. The higher the STC rating, the better a ceiling is at blocking sound. It’s more technical than that, but we’ll save that for the civil engineers reading this. For the rest of the article, we're just going to stick to calling it STC rating because that's what we use across the entire website when discussing airborne noise.

This is a measure to rate how well a ceiling can block airborne sound between adjacent spaces. There’s actually a way to measure how effective a ceiling is at blocking airborne noise, it’s called the STC Rating (sometimes given a more specific term of Ceiling Attenuation Class or CAC). Without an effective barrier, you won’t be able to relax in the room you’re trying to enjoy some quiet time in. Forcing that path allows your barrier to do its job, as THROUGH IT is the only option sound has. You want the sound waves to travel through the air until they collide with something like the floor in the room above you, at which point some of the waves create vibrations through whatever it runs into and into whatever’s on the other side. That’s why airtight construction is so key – airborne sound waves find the path of least resistance to travel from space to space. Sound waves move like water they flow towards the weakest point. For instance, loud talking, music or TV, a dog barking – these are all sound waves traveling through the air and then heard when they reach your ear. Airborne noise is just sound that travels through the air.

Sound deadening gypsum board