What is STC?

Almost all soundproofing products have a STC rating.

The Sound Transmission Class (STC) is a single-number rating of a material's or an assembly's ability to resist airborne sound transfer at the frequencies 125-4000 Hz. In general, a higher STC rating blocks more noise from transmitting through a partition. Exciting stuff hugh!

This video explains what STC or Sound Transmission Class is and how it is measured.

Soundproofing Walls - What is STC? - Funny video clips are a click away