Looking for Floor Soundproofing Underlay and Understanding IIC & STC Sound Testing?

Floor Soundproofing Underlayment

The floor covering industry considers the sound insulation very important in living areas such as multi-family or single-family dwellings. When evaluating flooring underlayment, sound deadening and acoustical ratings are one of the things homeowners or HOA considers. It all begins with how sound is generated and the medium it transfers through. The main test done by flooring industry is the Impact Insulation Class (IIC) ad Sound Transmission Class (STC). So lets first determine what these two test are.

Impact Insulation Class (IIC) Sound Rating

IIC test the ability to block impact sound by measuring the resistance to transmission of impact noise or structure-born noise. Examples include objects falling on floor, kids jumping off couches, tap dancing, anything that stimulates footfall.

Sound Transmission Class (STC)

STC evaluates the ability of a specific construction assembly to reduce airborne sounds. Examples include voices, stereo systems and TV noise.

So How Are The Ratings Calculated?

Both test involve an apparatus in an upper chamber and a measuring system in the lower chamber. The frequencies are calculated by decibel measurements and ratings are calculated by a very complex mathematical formula.

The higher the number, the higher the resistance – the better.

To meet International Building Code – both IIC and STC need to meet the minimum of 50 to pass. Many larger luxury condo associations and municipalities are now looking at the higher 50’s and lower 60’s range.

Floor Soundproofing Underlay Types

Knowing What Installation Type Of Your Floor Can Steer You In The Right Direction

Nailed Down or Glue Down Flooring

Nailing down your flooring to the subfloor is not the best option. When an impact is made on the floor, the impact energy will transfer to the nail to the subfloor.

Glue down is a better option due to no impact energy transferring to the subfloor but the underlayment.

View sound ratings for glue down and nail down flooring

Floating Engineered Wood or Laminate Flooring

With floating wood floors such as laminate, floating bamboo, rigid PVC core vinyl planks and wood/plastic; the underlayment is not attached to the subfloor or floor. There is a small air gap allowing to absorb more “sound”. The QuietWalk underlayment provides very high ratings such as IIC of 71 and STC 66 as of mid 2018.

Disclaimer: All Ratings Are Not Equal As with any underlayment sound testing number that a company gives you, each subfloor or floor assembly in your home. On top of that, the manufacture of the floor covering can use different materials. MP Global provides sound testing on common assembly but can not provide testing for every flooring in the world as it is entirely infinite.

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