The behavior of noise transmitting through a common floor/ceiling assembly system is not unlike that of the sound wave transmitting through a common wall as we outline in our course on Sound Transmission. The difference is that a floor/ceiling assembly combats more structure borne sound generated from footfalls and other movements up above. To break the energy path and force the collapse of the structure born sound wave, our goal is to either raise the floor up above, or lower the ceiling down below to generate the disconnect required to force the collapse.
Unlike a wall treatment, where our goal is to trigger a stronger STC value, a floor/ceiling assembly is rated by both the STC and what is called an IIC value. The IIC stands for Impact Isolation Class and is featured in its own course here at the Academy. The higher the IIC rating, the greater the isolation of impact-generated sound will be between two rooms. All newly constructed modern day multifamily dwelling units are required by building code to provide a minimum IIC rating of 50.
Sound reducing floor underlay treatments will typically target new build or remodel scenarios only. For clients with existing floor surfaces with no ability to apply underlay material, their only recourse is to lower the ceiling down below as we outline in our course on Ceiling treatments. With either technique, disconnection can be triggered. However, as we note in our course on Transmission Loss treatments, “flanking” paths will deteriorate the results of either technique. These will be any openings left untreated for sound control. They include light cannisters, vents, pipes, outlet plates, exhaust fans, doors, windows and a host of other openings in a room that will let noise escape despite you treatment. There are typically more openings in a ceiling (speakers, recessed lights, exhaust fans, etc) than there is on a floor surface. Therefore flooring treatments will typically outperform a ceiling treatment.
For new build or remodel projects where flooring has yet to be placed, our goal will be to “float” the finished flooring surface up and away from the structure of the facility. This is accomplished through the use of NetWell’s FloorFighter underlay material. This product is a free floating material that is applied beneath most any flooring substrate or carpet to help combat the bleed of noise and improve your IIC and STC ratings.
See FloorFighter Back to Sound 101