By Bob Pratt Director of marketing, MP Global Products
Reported sound test results for laminate underlayments can be somewhat confusing and even, perhaps, misleading. There are three different laboratory tests for sound vibrations traveling from one living area to another:

1. Impact Insulation Class (IIC). IIC evaluates the ability to block impact sound by measuring the resistance to transmission of impact noise or structure-borne noise (simulating footfalls, objects dropped on the floor, etc.).

2. Delta IIC. Delta IIC consists of two IIC tests, one for 6-foot concrete and the other for that same 6-foot concrete with underlayment and laminate included. The difference between those two readings is the delta or “change-in” IIC. Delta IIC provides a more direct method to evaluate the impact sound deadening characteristics among different underlayments.

3. Sound Transmission Class (STC). STC evaluates the ability of a specific construction assembly to reduce airborne sounds, such as voices, stereo systems and TV.

Non-laboratory, “field” tests for impact sound (FIIC) and airborne sound (FSTC) are also available. These sound tests utilize the same testing methods as IIC and STC but are conducted in an actual building after the floor installation is completed.

The International Building Code (IBC) suggests ratings of 50 or higher for both IIC and STC, and ratings of 45 or higher for FIIC and FSTC testing.

It is important to note that IIC/FIIC and STC/FSTC tests are not single component tests, but an evaluation of the whole floor/ceiling assembly, from the surface of the floor covering material in the upper unit to the ceiling in the lower unit. An integral part of a report for any of these sound tests is a detailed description of the floor/ceiling assembly used in the test. IIC/FIIC and STC/FSTC tests are essential tools for evaluating sound in multi-level dwellings. However, without knowing and accounting for the whole floor/ceiling structure used in the test, the results are basically meaningless.

Using IIC (FIIC) and STC (FSTC) results to represent the sound-deadening ability of an underlayment without describing, in detail, the whole floor/ceiling assembly used in that testing causes confusion at all levels of the marketplace and is ultimately misleading to the consumer.