With the formulation of sound insulation performance standards by the Architectural Institute of Japan in 1979, the sound insulation ratings for floor impact sound level determined by means of the heavy and soft impact source stipulated by JIS have been used for performance orders and labeling for buildings in general. Furthermore, prediction calculation methods for sound insulation ratings based on the impedance method have also been developed. This has led to an increase in the thickness of standard floor slabs in concrete apartment houses in Japan from 110--120 mm at that time to 150--160 mm and, recently, there are many floor slabs that are as thick as 200 mm, thereby greatly contributing to an improvement in floor impact sound insulation performance. Meanwhile, there has also been progress in research dealing with the improvement of the insulation performance of heavy floor impact sound in wooden buildings. Unitizing highly rigid floor panels and beams and increasing the flexural rigidity of the overall floor cross section, while designing sound-insulated ceilings of the lower storey independent of the floor structure and the independent walls of the room below, have made it possible to achieve the performance of a concrete slab about 150 mm thick.