## 6 Conclusions  
In this study, a series of field measurements were carried out to examine the current situation regarding the water supply and drainage noise in the bathrooms of the multi-residential buildings of Korea. The number of studied housings is 64, and they comprise 14 different floor plans. The water supply and drainage noise were measured in the bathrooms of the lower floor according to the different operations of each sanitary ware including the water closet, basin, and bathtub. The noise levels were also measured in the bathrooms of the upper floor and the adjacent rooms of the lower floor for 11 housing units with different floor plans. The measurement parameters in this study are therefore as follows: (1) noise level in the bathroom of the lower floor (\(N\) = 113); (2) noise level in the bathroom of the upper floor (\(N\) = 19); and (3) noise levels in the living room (\(N\) = 11) and bedroom (\(N\) = 8) of the lower floor. The time history of the measured SPL from the use of each sanitary ware displayed strongly fluctuating noise levels for the water drainage, while it is rather continuous for the water supply. Also, the water supply and drainage noises produce relatively high SPL values at 500 Hz and 1000 Hz, respectively, compared with the other frequencies. Figure 14: Frequency distribution and cumulative percentages of water supply and drainage noises (L\({}_{\rm{AFmax}}\)) in the living room (\(N\) = 11) and bedroom (\(N\) = 8) of the lower floor from the use of the sanitary wares. The measurement results in the bathrooms of the lower floor (\(N=113\)) showed that the highest noise level is 47.8 dBA on average for the water drainage noise from the use of the water closet. The second ranking comprises 42.7 dBA for the water drainage noise from the use of the basin, and then 33.9 dBA was measured for the water drainage noise from the use of the bathtub. The water supply noise ranged between 33.7 dBA and 37.0 dBA. The above results suggest that the priority for noise control is in the order of water drainage from the water closet, water drainage from the basin, and water supply to the sanitary wares, as well as water drainage from the bathtub. The frequency distribution and cumulative percentages of the water supply and drainage noises in the bathrooms of the lower floor suggested that the maximum noise level is concentrated between 46 dBA and 50 dBA, thereby deriving the average noise level of 47.7 dBA. The minimum and maximum noise levels ranged between 41.3 dBA and 60.1 dBA. According to the different construction methods of the bathrooms, the UBR system produced a noise level that is lower than that of the wet-construction method for all of the operational conditions of each sanitary ware. The highest noise level for the UBR system is 42.8 dBA, while it is 48.2 dBA for the wet-construction method. The altitude of the housing has an insignificant influence on the variation of the noise level. The highest noise levels in the living room (\(N=11\)) and bedroom (\(N=8\)) of the lower floor are 34.3 dBA and 39.1 dBA, respectively, for the water drainage noise from the use of the water closet. The frequency distribution and cumulative percentages of the maximum noise level in the adjacent rooms was concentrated at approximately 37 dBA, thereby deriving the average noise level of 37.8 dBA. The overall results suggest that the current situation of water supply and drainage noise in the multi-residential buildings of Korea meets Class C (living room) and Class D (bedroom) of the 2 nd ISO/CD 19488, although some of the measurement data from the rooms are outside of the minimum limit; however, it is still necessary to develop the acoustic guidelines to satisfy the higher class for the creation of a comfortable residential environment. This work was supported by the 2016 Research Fund of Korea Land and Housing Corporation (R201605003). [PERSON] conceived and designed the experiments; [PERSON] and [PERSON] performed the experiments; [PERSON] and [PERSON] analyzed the data; and [PERSON] wrote the paper.