## 4 Results
### Noise Level in the Bathroom  
The water supply and drainage noises were measured in the bathrooms of the upper (\(N=19\)) and lower (\(N=113\)) floors according to the use of the sanitary wares including the water closet, basin, and bathtub. Figure 7 shows an example of the frequency spectrum in one octave band for the water supply and drainage noises measured in the bathrooms of the upper and lower floors for the 59A type. The frequency spectrum was analyzed for the noise level measured in L\({}_{\rm AFmax}\) during the operation time of each sanitary ware. The results show that the use of the water closet generates a relatively high noise level in the bathrooms of the upper and lower floors compared to the basin and bathtub. Generally, the three sanitary wares produced strong sound energies at middle and high frequencies above 500 Hz in the bathroom. It is expected that the high noise levels at the middle and high frequencies cause more sensitive subjective responses due to the use of the sanitary wares. Figure 5: Time history of water supply and drainage noises from the use of sanitary wares including the (**a**) water closet, (**b**) basin, and (**c**) bathtub measured at different locations (only a part of the time history has been shown due to long-time operation). Figure 6: Time history of the noise from the use of the water closet installed in 19 bathrooms of 11 housings with different floor plans (longest time with red dot: bathroom attached to the living room of the 59A type; shortest time with green dot: bathroom attached to the bedroom of the 84A type). Figure 7: Frequency spectrum of the water supply and drainage noises (L\({}_{\rm AFmax}\)) from the use of the sanitary wares in the bathrooms attached to the living room of the upper and lower floors for the 59A type: (**a**) water closet; (**b**) basin; (**c**) bathtub. Figure 8 shows the average noise level from the use of each sanitary ware measured in the bathrooms of the lower floor attached to the living room (\(N\) = 64) and bedroom (\(N\) = 49). The results show that the highest noise level is 47.8 dBA for the water drainage from the use of the water closet in the bathroom attached to the bedroom. The noise level of the second ranking is 42.7 dBA for the water drainage from the use of the basin in the bathroom attached to the bedroom. The water supply noise shows similar levels approximately between 33.7 dBA and 37.0 dBA for all of the sanitary wares. The deviation bar indicating the range between the maximum and minimum noise levels implies that the noise level is different according to the studied housings with different plans. The graph in Figure 9 shows the frequency distribution and cumulative percentage of the maximum noise level in 113 bathrooms of the lower floor according to the water supply and drainage noises of the three sanitary wares. It can be seen that the maximum noise level is concentrated between 46 dBA and 50 dBA. The lowest value of the maximum noise level is 41.3 dBA, whereas the highest value is 60.1 dBA. The average value of the maximum noise levels measured in the 113 bathrooms is 47.7 dBA. The results indicate that most of the residents living in the lower floor can recognize the noise in the bathroom due to the use of the sanitary wares in the upper floor because the S/N ratio is approximately 30 dBA if the background-noise level is assumed to be 20 dBA. One of the major factors determining the noise level could be the construction method of the bathroom. In this study, the UBR system has been applied to the floor plans with a small floor area less than 46 m\({}^{2}\), while the wet-construction method was applied for the larger floor plans. Figure 10 shows the average noise level for the water supply and drainage of each sanitary ware according to the construction methods, including the UBR system (\(N\) = 15) and the wet-construction method (\(N\) = 97).