The acoustic impedance and absorption characteristics were investigated for open‐celled urethane foams with and without surface coatings. The variables considered were the foam thickness, cell size and density, and the coating material mass and thickness. The application of thin films of area density in the order of 0.005 g/cm2to the foams resulted in an increase in the absorption for the foams of12and 1 in. thickness with variable results for foams of 2 in. thickness. The addition of coatings of density in the order of 0.05 to 0.45 g/cm2increased the absorption at a frequency of 240 cps but otherwise decreased the absorption. The results were essentially independent of the nature of the surface coating and, within limits, depended largely on the surface mass per unit area. Also noted was an absorption increase which was attributed to the vibrating of the surface material in one of its natural modes.