Study of the acoustic transmission characteristics of a pipe opening with a baffle considering structural elasticity

Noise can radiate to the external environment through pipe openings. The acoustic transmission characteristics of the pipe openings greatly affect the efficiency of sound radiation. In fluid-filled elastic pipelines, the sound radiation is significantly influenced by the coupling between the fluid and the elastic structure. The elastic structure studied in this paper includes the pipe wall, as well as the baffle attached to it. Waveguide analysis of fluid-filled elastic pipelines shows that the coupling results in the presence of several types of propagating waves within the pipeline, even bellow the cut-on frequency. To evaluate the acoustic transmission characteristics of the pipe opening, it is necessary to separate the components of the lowest-order fluid type wave from these waves. A multi-case approach is developed to separate the target waves successfully, thereby obtaining the characteristics of the pipe opening. The accuracy of the proposed method is verified, and the impact of structural elasticity is analyzed. Subsequently, the effects of the dimensions of the baffle are discussed.