A description of a tube method of determining the sound absorbing power of materials in which no exploring device is introduced in the path of the sound wave in the tube. The method is an extension of a research by Kennelly and Kurokawa on “Acoustic Impedance and Its Measurement,” and makes use of the motional impedance of a telephone receiver which serves as both the source of the sound wave in the tube and as the means for determining the fraction of sound absorbed by the material, a sample of which is attached to the piston which slides in the tube. Sample calculations for sound absorption are included.