Sound transmission through a double – wall circular cylindrical shell is investigated. In order to study the acoustic behavior of these kinds of thin circular cylindrical shells, an exact analytical approach is discussed in detail. Using an infinitely long thin walled circular cylindrical shell subjected to a plane wave incidence, the structure – acoustic equations based on the Donnell’s thin shell theory are obtained and transmission losses calculated by this approach are compared to the transmission losses obtained according to the Love’s theory. The comparison shows that the Donnell theory distinguishes all the frequencies in which sound transmitted inside the shell easily and it predicts the sound transmission characteristics of a thin circular cylindrical shell better than the Love’s theory especially in resonance – controlled and mass – controlled regions. Then the effects of different sound absorber materials and various gases are studied in order to fill the cylindrical shell’s gap with a material except air. The results show that high sound transmission loss and better trend can be achieved by using these sound absorber materials in double-wall circular cylindrical shells.