Abstract
The strong potential of porous media to absorb and change an incident sound wave interacting with a fluid that fills the pores of the material has sparked interest in their acoustic properties. Therefore, the current study describes the energy distribution and absorption mechanism of a dominating acoustics wave mode traveling out of the mouth of a semi-rigid waveguide. The underlying structure is tuned due to a trifurcated inlet region with flexible outer boundaries. In the outlet region of the duct, porosity effects for different porous materials are encountered. The continuity of pressure and velocity through the interface is used to match the scattering orthogonal and non-orthogonal duct modes. Mode matching techniques are used to compute the reflection and transmission coefficients. The resulting infinite linear algebraic systems are truncated and numerically solved. Of particular interest, the effects of considering different porous materials are observed and analyzed thoroughly. The obtained solution is confirmed to satisfy all geometrical conditions as well as the law of conservation of energy by mathematical and graphical representation.