In the application of fluid-saturated porous materials to the absorption of sound it is assumed that the attenuation is enhanced by increased relative velocity between the solid matrix and the fluid. Foamed metals are expected to have a structure that is more rigid than that of other porous materials with larger concomitant absorption. The bulk modulus of such a material was measured in an acoustic coupler filled with castor oil. The viscosity was varied by changing the temperature from 0° to 30°C. Two foamed aluminum samples were used; the first with density relative to that of solid aluminum of 10.1% and 8 pores per cm, the second with relative density of 14.5% and 16 pores per cm. The frequency range was from 100 to 3000 Hz. The pressure was varied from 2 to 20 MPa. The measurements are represented as a complex bulk modulus relative to that of castor oil (assumed lossless), versus the inverse Stokes number, which combines frequency, pore size, and viscosity. The experimental points for the various values of these parameters show satisfactory agreement, and there is a noticeable trend in the variation of real and imaginary parts as a function of the inverse Stokes number. [Work was supported by ONR.]