Acoustic wave propagation and attenuation in catalytic converters are investigated in the present study. The relationships for wave propagation in a catalytic monolith are derived first and then coupled to the wave propagation in tapered ducts which are commonly placed at either end of the monolith. Analytical and finite element approaches are used to solve the resulting coupled system of equations. Theoretical predictions are then compared with the experimental results for two different (one circular and the other oval) catalyst configurations. The attenuation characteristics of the catalyst with and without the monolith are also investigated.