Interior noise factor plays an important role in today's customer' preference for vehicle brands. All car manufacturers and suppliers develop their investment in this respect. Today's changing needs and the competition having taken place among car manufacturers cause the isolators to be constantly upgraded. It is possible to use various methods to determine the sound absorption coefficient of the isolators. In this study, five isolators that have the same thickness and different structural features and that are to be used in a specific location of the car were selected, and their sound absorption coefficient were measured using an "Impedance Tube". The results obtained were compared to each other, considering the structural features of the materials, and the changes they created in the internal noise were also analyzed.