A noise-reducing substrate for use in a flooring system which ha a subfloor and a floating floor upper layer. The substrate comprises a series of edge butted panels, each having a bottom surface, a top surface and side surfaces. A profile in the bottom surface of the substrate changes the substrate's effective stiffness improving the noise isolation of the substrate compared to the stiffness and noise isolation of the panel without the profile. Additionally, the profile reduces the weight of the panel, thereby reducing manufacturing and installation costs. Material hardness and profile flatness of the upper surface provide the strength and texture required to allow for installation of the floating floor layer without the need for an additional rigid backing material. Such a system greatly improves the impact noise reduction on floor/ceiling systems while keeping the installation cost low and adding little to the total system thickness.