New research demonstrates that the use of properly specified separate carpet cushion, expressly designed for commercial applications, can deliver as much as double the sound absorption of glued-down carpet alone. The acoustical research, jointly sponsored by the Alliance for Flexible Polyurethane Foam (AFPF) and the Carpet Cushion Council (CCC) and conducted by Intertek Testing Services (ITS), measured the sound-absorbing capacity of commercial cushion under carpet. Noise Reduction Coefficient (NRC) is a measure of the effectiveness of a material in absorbing sound over several frequencies.
“Our computer measures how long it takes for noise to dissipate in a room,” explains ITS’ Mark Keller, who conducted the research. “We generate a brief, loud noise, first without any carpet, then with a glued-down carpet sample, and thirdly, with a sample of carpet cushion installed under the carpet. We measure the different times the noise takes to dissipate to determine the percentage absorbed.”
The tests revealed that cushion plays a critical role in sound absorption. A commercial cut-pile carpet product direct-glued to a concrete substrate yielded an NRC of approximately 0.25 (1.0 represents 100-percent sound absorption). When a commercial bonded polyurethane carpet cushion was installed using a double-glue system with the same carpet, the NRC rose to 0.55. The sound absorption was more than twice that of the carpet alone.
“Using a cushion under carpet in commercial buildings should become standard practice, just as it is in residential buildings,” says Bill Wald, CCC technical director.
Testing in two rooms, one upstairs and one downstairs, also measured the ability of carpet with cushion to lessen the sound transmitted between floors through the Impact Isolation Classification (IIC) test. A bare concrete slab, with an IIC rating of 19, improved to 58 with the addition of direct-glue carpet. When the same carpet was double-glue installed with bonded commercial polyurethane carpet cushion and tested, the IIC rating increased to 69.
The remarkable degree of acoustical improvement that was measured is of particular interest to facility managers who seek to increase productivity by assuring a quieter environment. From its origin, sound moves through a building in pressure waves, like the ripples from a pebble tossed into a pond. The objective is to control these pressure waves, typically by materials such as cushion under carpet that will absorb the waves before they reach people in their working environment.
For a full report on carpet cushion acoustics testing, download the white paper Sound Absorption in the Workplace at (www.afpf.com), or call the Alliance for Flexible Polyurethane Foam directly at (800) 696-AFPF (2373).
Mike Norton is principal at Dalton, GA-based Norton Performance Consulting.