Sound insulation characteristics of two‐layered cylindrical shells partially exposed in a free field

This paper is concerned with the sound insulation characteristics of two‐layered cylindrical shells excited by a plane acoustic wave propagating axially within the shells. The shell has an infinite length; however, it is exposed in a free field by the length L. It is otherwise covered with rigid baffles. Each layer of the shell is assumed to bend according to a thick‐shell theory, and the two sets of the shell equations are combined together through the continuity conditions of the displacements and tractions at the interface of the layers. The air surrounding the shell is described by the Helmholtz linear acoustic equation. The transmission loss through the shell wall, TL, is derived and calculated for various values of the physical parameters involved.