Sound insulation performance of prefabricated cabins in cruise ships

In this paper, sound insulation performance of a prefabricated cabin mock-up is studied. The cabin mock-up consists of two identical rooms whose partition, ceiling, and side walls are sandwich panels composed of thin metal sheets and mineral wools. The floor is a steel plate with stiffeners, and plate thickness is 6 mm. It is shown that sealing gap between the floor and the partition improves STL (Sound Transmission Loss) significantly above 2000 Hz. Even after all gaps are sealed, the weighted sound reduction index R_w of the partition measured in the mock-up is lower than that from laboratory measurement by 9 dB. To find out how flanking transmission of noise degrades R_w of the partition, we measure structure-borne noise (SBN) of room surfaces. It is found that SBN of the steel floor is the most important factor in flanking transmission of SBN. Although SBNs of sandwich panels in the source room are larger than that of the floor, they decrease rapidly as they propagate to the receiving room, because sandwich panels provide considerably more damping than the steel floor. Consequently, SBN of the floor becomes dominant in the receiving room. Statistical energy analysis is performed, where SBN transmission along the floor is investigated. It is concluded that that the most effective way to reduce flanking transmission of SBN is to increase damping of the floor.