Each building is different and therefore any acoustic treatment of floors in any building needs to be considered in relation to the structure, age and existing acoustic properties of the building.
Testing the sound levels involves determining the Impact Insulation Class (IIC) rating and is usually done via ‘Tapping Testing’ Noise is generated by placing a standardised “tapping machine” on the floor and measuring the sound pressure levels are measured in the room under at several different frequencies.
A standard tapping machine with five–steel faced hammers strikes a test floor material, generating sounds between 125 Hz – 4000 Hz. The impact creates vibrations that travel through the flooring and produce sounds on the other side. Depending on the amount of impact sound that is lost during the transmission, the results from each tap are plotted on a graph. Depending where those points fall on the graph, they are compared to a reference and the IIC rating is determined. The sound levels are corrected to account for the acoustical properties of the receiving room.
The IIC rating can be tested in one of two different environments: Each floor covering product can be tested individually and given an IIC product rating based on that test, or can be tested as part of an entire floor/ceiling assembly. The latter can include not only the floor covering (carpet, hardwood, tile, etc.), but also the subfloor, underlayment, flooring joists, ceiling below, as well as adhesives and sealants that may be needed for installation. In addition, there are plenty of other sound–deadening materials that are used in floor/ceiling assemblies. For example, fiberglass insulation and resilient channels can be used to increase an IIC rating. In these tests, the entire floor/ceiling assembly works together to result in the structure's overall IIC rating.
The most appropriate and accurate way to measure the IIC of a home or building is to do so after installation. This way, all materials are taken into account for and given a total IIC value. Also, any air vents or other obstacles that sound can travel through are also accounted for with this method. This method is also known as the Field Impact Insulation Class (FIIC).