1. More resilience, more vibration absorption.
2. More void equals less touch and less vibration wave conduction.
3. Thicker materials equal greater ability to handle larger vibration waves.
All of these qualities need to be weighed against the finished floor’s structural needs. Highly resilient products do not work with ceramic tile or VCT but might be fine for engineered wood. Products with lots of void space provide limited structural support for direct fastening flooring and sometimes require a mortar bed, plywood substrate or gypsum underlayment. Most often, manufacturers provide ASTM standard Robinson Wheel Test results to prove acceptability in the application. Look for products that have these tests available.
Concrete construction provides a structure with great dynamic stiffness. Wood frame projects are much more bouncy. The noise problems in concrete construction are typically high frequency. In wood frame, the bounciness leads to low frequency problems. The solutions in wood frame cannot always be found in a topically added mat installed by a flooring contractor. One important check - the level of deflection and minimum design standard is L/360. Mass elements like floor joists and underlayments need to be stiff, and resilience or bounciness is very bad.
In concrete, that solution typically can be found with one good roll added to the topside of the concrete. But, all concrete construction is not the same. An 8-inch concrete slab is not the same as a 4-inch concrete corrugated deck. The noise performance is a function of the stiffness, and consequently the slab thickness. Additionally, ceiling design is very important. No ceiling and the mat on the topside of the concrete is the only sound element. That burden means a substantially thicker, more resilient, more void sound product is required. Contractors are not responsible for identifying expectations of owners, nuances of condo associations or conforming to building codes. That means guaranteeing the performance in contract documents must be redlined.
So, what do I do differently? Or, what do I do when I bid a project? First, pass the sniff test for the products. That means if the material is rigid and is totally solid (isn’t thicker than a 0.03125” fabric), don’t buy the performance. If the material has some sponginess, has the supporting test data on acoustics and on structural questions, have some faith. Don’t put your name on the line if it doesn’t.
Now that you know how it works and understand your role, don’t be surprised when the acoustical consultant shows up to see how it performs. That happens in California all the time. In fact, in some areas of the country, it is a required step before a developer gets an occupancy certificate. Imagine that any room, any unit can be the tested location. Now you know the role, the stakes, and better yet, what makes things work and succeed. Sounds good, doesn’t it?