Recently, studies are very active on the prediction of the acoustic characteristics of the catalytic converters in automotive exhaust systems. The monolith of catalytic converters is composed of a bundle of capillary tubes in which the viscothermal effects on the wave propagation are very important as well as the convective ones. Sound attenuation in the turbulent pipe flow or variational method using the parabolic velocity and temperature profiles have been proposed as analytical models for this problem, while FEM is attempted for more precise analysis. In this paper, the linearized governing equations are solved by the recursive use of the Runge-Kutta and shooting method considering the radial velocity component. Characteristics of the forward and backward waves are described along with the shear wave number varying the flow Mach number, and the results are compared with the previous works. It is shown that hydrodynamic waves are generated with steady flow and they are attenuated more than the acoustic waves. In addition, an acoustic model is developed by considering the effect of wall porosity. It is observed that the measured transmission loss of a porous sample agrees very well with estimated one in the absence of mean flow.