Sound Transmission Loss of a Two-Layered Pyramidal Structure Lined with Porous Material

Abstract

This paper presents a theoretical model based on Biot theory to investigate the sound transmission loss (STL) of a pyramidal lattice sandwich structure lined with porous material. This theory is more accurate than equivalent methods and suitable for use in different complex filling configurations. Several filling patterns with different boundary conditions are studied, and their governing equations are derived by presenting the exact displacements and stresses for both solid and fluid fields. The models are validated by comparing with available literature and simulation results. The numerical results show the influences of porous materials, their structure on the STL, and their mutual inhibitions. In addition, it is found that different parameters dominate in different configurations and frequency ranges. These results reveal the interrestricted relationship between the STL and its bearing capacity. Moreover, the external mean flow condition inspired by real-life situations is studied to analyze its effects on sound transmission. These results show that the STL depends on the flow directions, and a critical value of the Mach number exists in the upstream situation.