A BS TRA CT An acoustic laboratory has been constructed in order to measure sound transmission through.floors. It has been erected inside hn existing building. Apart.from the costs being considerably less than (f a new building had been constructed, this has meant that several other advantages have been obtained. The design and location of the laboratory have been partially governed by activities already existing in the building. This article presents the construction from the point of view of building technique and of acoustics. In an effbrt to eliminate flank transmission in the frequency range 100-3150 Hz the construction has been dimensioned with vibration dampers having a natural frequencyfo = 10 t:lz. For the same reason and in order to increase the sound insulation the walls and ceiling have been lined with radiation reducing material Comparative calculations and measurements have been carried out which show how the results have been affected by this procedure. The radiated eff'ect from the various surfaces is shown in the form of graphs. The ratios of the receiving room dimensions are chosen so that the natural frequencies in the low-frequency region 100, 125 and 160 Hz are spaced fairly uniformly Despite the economk' limitations and a limited amount of space the laboratory meets the requirement set by the International Standards ISO 140 with a good margin.