In this paper, a new method is proposed for the measurements of sound insulation of light structures using small samples. The sound source is placed in a reverberation room, and the receiving room is a small anechoic box. The arrangement of the measurement is described in betail. Several samples are measured and the results agree well with the mass law. The method does provide a useful alternative where the measurements for the samples of small dimensions with high transmission loss are required. Limitations of the equipment and evaluation of accuracy are also discussed.