Understanding the behavior of acoustic materials in engineering applications requires characterizing their absorptive properties. The impedance tube can be used to measure the absorptive properties of the specimen, such as the normal incidence, sound absorption coefficient, and estimate the normal incidence surface impedance and flow resistivity. The impedance tube of 1 m length was modeled in ANSYS Mechanical APDL using the 2D acoustic element FLUID29, a linear element with optional displacement degrees of freedom.