In this study, polyurethane (PU)/nano-silica nancomposite foams were prepared. The effects of isocyanate index, cell size, density, and molecular weight of polyols on the sound absorption ratio of PU/nano-silica foams were investigated. With increasing nano-silica content, the sound absorption ratio of PU/nano-silica foams increases over the entire frequency range investigated in this study. Decrease of isocyanate index, cell size, and increase of density leads to the increase of sound absorption ratio of PU/nano-silica foams. PU/nano-silica foams have a broad T(g) centered around room temperature by decreasing molecular weight of polyol resulting in good sound absorbing ability. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 2384-2390, 2012