A number of coatings are available for application on smooth materials for greater sound protection. Because these coatings are thin they may not provide as much protection as other options, but in a noisy environment the difference can be appreciable. Spectrum undercoatings, for example, are designed to be painted on sheet metal for reduced sound. Epoxy-based coatings can be used on a variety of materials around the house for similar dampening.
When it comes to sound-deadening, cork is often the material of choice. The porous, woody flooring absorbs sound waves instead of propagating them. But cork needs a protective layer of its own to keep it from peeling apart over time. If your cork did not receive an acrylic seal in the factory when it was first made into panels, buy a cork sealant and use it to increase durability and sound protection.
Pastes are similar to coatings but are thicker compounds designed for even greater sound protection. You can change the thickness of the paste to control how much soundproofing you want. The pastes may be available in different levels of thickness as well. These pastes may work well as part of subflooring and under-floor remodeling projects if you have a serious sound issue, especially in factories or buildings.
For a basic and easy-to-install type of flooring, there are acrylic foams and mats you can buy for soundproofing capabilities. This is especially useful if you have not already installed the flooring but still want to dampen sound. You can install the mats over the subfloor and then glue or nail down your flooring on top of them for added insulation and noise absorption.