US Patent 7886488 Acoustical isolation floor underlayment system

An acoustic isolation medium configured for placement between a subfloor and a finished floor with a poured underlayment, includes a first layer being a sound reduction mat disposed upon the subfloor, a second layer placed upon the first layer and being one of a sheet of fibrous material and a web of limp mass material with a high internal damping coefficient, and a third layer placed upon the second layer and being the other of a sheet of the fibrous material and a web of the limp mass material.