Sound transmission loss ( TL ) is the quantity which indicates the sound insulation performance of board materials or the wall structure. It has widely been used for construction materials such as wall panels or doors, and automobile parts such as doors or dashboards. The measurement is implemented by setting up a sample between two measurement rooms, "Source Room" and "Receiving Room", and the TL is calculated from the comparison between the incident power into the sample and the transmission power through it. To obtain input and trasmitted power, we need to measure several points in each room. If the microphone is moved manually, the measurement would be a very time-consuming job. With this system, it can be moved automatically by using the microphone traverse system. Thus, a large amount of labor hours for measurement is saved.