A new acoustic method for directly measuring the flow resistance, and the compressibility of fibrous materials such as glass wool, is given. Measured results for monochromatic sound in glass wool are presented and compared with theoretically calculated results. The agreement between experimental results and theory is good. Results of measurements of characteristic impedance, attenuation, and phase shift for plane monochromatic traveling waves are presented and compared with theoretically calculated ones. Good agreement between experimental and theoretical results was found.