US Patent 8347575 Lightweight acoustical flooring underlayment

An acoustical flooring underlayment for placement between a subfloor and a finished floor, includes a mat having an upper surface, an opposite lower surface and including a plurality of corrugations creating a plurality of depressions in the upper surface. A layer of foam is applied to the upper surface and constructed and arranged to fill the depressions for creating a generally planar top surface configured for accommodating the finished floor.