The paper presents calculations of characteristics at the various configuration of a silencer, reflecting the influence of various parameters on its performance result. The basis of the technique by which the corresponding calculations were carried out is the use of an integral indicator of the acoustic performance of silencers. The significance of the method of impedance setting in the software system COMSOL Myltiphysics, a silencer location in the exhaust pipe and its length on the final performance is shown. The performance of silencers was assessed using the unmuffled noise spectrum as input data.