Noise Reduction Laminate Underlay
Most of us have walked on a laminate floating floor and commented on the rather annoying clicking sound that tends to emanate from the traffic. Traditional foam underlay will help to somewhat reduce this noise, but more sophisticated sound control underlayments like Quiet Walk, Silent Walk or SilentStep will be much more effective.
Do NOT purchase "No Underlayment Laminate Floor" that has a pre-applied underlay attached to the back side of the floor, if you intend to use a noise reduction product. Doubling up of the foam will cause tongue breakage and lead to floor separatation.
In the condominium construction sector, the building code actually specifies a required level of noise reduction underlay that must be used to guarantee reduced noise transmission between floor levels. Laboratories have come up with a testing and measuring procedure that helps builders know if they have achieved the necessary level of sound control and complied with these building code standards. STC and IIC are two of the measuring sticks.
Sound transmission Class (STC): is used as a single number indicator to rate how well materials block airborne sound. Testing procedures used traditional household and office noise in the frequencies most common with TV's, radios, office equipment and the human voice, as the basis of the test.
A STC rating of 30 suggests that this material and installation will block an average of 30dB of noise from transmitting to the floor below, but this is only a generalization as a product can be very effective in noise control over the range of frequencies as suggested above, and yet be next to useless in stopping low frequency thumping of your son's stereo. Thus if you are serious about noise attenuation your installation must factor in onsite specifics associated with the range of frequencies expected.
Impact insulation Class (IIC): Impact sound transmission tests are carried out using a standard tapping machine that uses 5 steel-faced hammers that strike the floor being tested. The tapping machine is placed in several positions on the floor and the impact sound pressure levels are measured in the room below in the frequency range 100 to 3150 Hz. This is a way to study how movement from daily foot traffic will transmit noise to the room below.
As with STC, the building code is specific in the minimum acceptable IIC rating that a nose reduction laminate underlay must attain for multilevel construction.
In the family home this is a matter of choice whether it makes sense to spend extra dollars to achieve a higher level of sound proofing. Historically the industry has used acoustical rubber underlay or cork underlayment as rather expensive answers to the problem, but in latter years the industry has created a line of more traditional foam underlays that achieve competitive STC and IIC rating without such steep cost increases.
Some would suggest it is a bit of overkill, but we each have our own priorities and budgets and with prices dropping for such products it may now make sense for some clients in the residential marketplace.
Here's a table I've put together showing the most common sound control underlayments available on the market that might be considered by the discerning client for residential applications.