1.8 Sound Transmission Class

What is a Sound Transmission Class?

It is a rating of how well a building assembly (partition construction) attenuates airborne sound.

Sound Damping Techniques

Typical interior walls in homes (2 sheets of 12.5mm plasterboard lining on a timber stud frame) have an STC of about 33. When asked to rate their acoustical performance, people often describe these walls as “paper thin”. They offer little in the way of privacy. Adding absorptive insulation (i.e. fiberglass batts) in the wall cavity increases the STC to 36-39, depending on stud spacing. Doubling up the plasterboard linings in addition to insulation can yield STC 41-45, provided the wall gaps and penetrations are sealed properly.

Practical Meaning of STC values

STC 25: Normal speech can be understood easily through a wall.
STC 30: Loud speech can be understood fairly well.
STC 35: Loud speech audible but generally not intelligible.
STC 42: Loud speech now is audible as a murmur.
STC 45: You need to strain to hear loud speech at all.
STC 48: Some loud speech is barely audible.
STC 50: Loud speech is not audible.

Rockcote STC Rated Products

50mm Integra Panel – 33