Sound Transmission Class – STC Ratings

Q: What is STC rating?
A: STC rating, or Sound Trasmission Class, refers to the amount of sound reduction a given floor has. This is typically a rating important to underlayments. STC rating is important to consider when installing laminate floors, as this can deaden the “clicking” or “hollow” sound laminate floors have when walking over them. This sound deadening can cause a laminate floor to sound closer to real floor wood floors. STC rating is also key to keep in mind for installing a floor in a condo or upper levels of a home. Home Owner’s Associations tend to require higher STC rated underlayments, such as 6mm cork or Sound6 Barrier Acoustical underlayments, to prevent sound from transferring to other condos in a complex.
This testing is typically done in laboratories using a suspended ceiling which is insulated, a 6 inch thick concrete slab, the underlayment, and flooring. A machine is used to tap on the flooring at various frequencies tot est how much sound is lost when transferring from the room over the suspended ceiling to the room below