Lightweight roofings made of metal and membranous materials are often used for buildings of large volume. In such cases, noise radiated from roofs excited by rainfall often causes serious acoustic problems. In order to investigate this problem, we developed an apparatus simulating natural rainfall which was reported in Part 1. With this apparatus, a series of sound power level measurements were performed under a strong rainfall conditions for 20 kinds of specimens and sound insulation performances were examined. In addition,the relationships between sound power level and sound transmission loss measured by sound intensity method was investigated statistically. As a result, it has been indicated that a linear relationship exist between them.
