## 3 Methodology
### Experimental Setup  
The noise levels for the water supply and drainage were measured in the bathroom and adjacent room of the multi-residential buildings. The equipment used for the measurement included a four-channel Harmonic system (0.1 dB) with \(\frac{1}{2}\)\" microphone (G.R.A.S. Type 40 AF) and preamplifiers (G.R.A.S. Type 26 AG), and the NA-28 portable sound level meter (RION). In the adjacent room including the bedroom and living room, the four-channel Harmonic system and one NA-28 were located at a height of 1.2 m. Four microphones were set up at the corner positions 0.75 m from the room surfaces. One microphone was placed at the center of the room. The noise level in the room was the average value measured over the five microphones. No furniture or other obstacles were in the room. The noise levels in the upper and lower bathrooms were measured using one NA-28 simultaneously \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Type of** \\ **Housing Unit** \\ \end{tabular} } & \multicolumn{2}{c}{**Dimension of the Bathroom (W \(\times\) D \(\times\) H (mm))**} & \multirow{2}{*}{**Construction Method**} \\ \cline{2-2} \cline{4-4}  & **Bathroom Attached to the** & & **Bathroom Attached to** \\  & & **Living Room** & **the Bedroom** \\ \hline
33 & 2440 \(\times\) 1740 \(\times\) 2080 (3.11 m\({}^{2}\)) & - & UBR system \\
36 & 2380 \(\times\) 1740 \(\times\) 2080 (3.06 m\({}^{2}\)) & - & \\
46 & 2110 \(\times\) 1710 \(\times\) 2080 (3.61 m\({}^{2}\)) & - & \\
59A & 2240 \(\times\) 1790 \(\times\) 2270 (3.62 m\({}^{2}\)) & 2290 \(\times\) 1640 \(\times\) 2270 (3.02 m\({}^{2}\)) & Wet construction \\
59B & 2240 \(\times\) 1790 \(\times\) 2270 (3.88 m\({}^{2}\)) & 2240 \(\times\) 1640 \(\times\) 2270 (3.07 m\({}^{2}\)) & \\
59C & 2240 \(\times\) 1790 \(\times\) 2270 (3.89 m\({}^{2}\)) & 2480 \(\times\) 1730 \(\times\) 2270 (3.00 m\({}^{2}\)) & \\
74A & 2340 \(\times\) 1790 \(\times\) 2270 (3.95 m\({}^{2}\)) & 2340 \(\times\) 1600 \(\times\) 2270 (3.56 m\({}^{2}\)) & \\
74B & 2340 \(\times\) 1790 \(\times\) 2270 (3.79 m\({}^{2}\)) & 2230 \(\times\) 1790 \(\times\) 2270 (3.83 m\({}^{2}\)) & \\
74C & 2390 \(\times\) 1740 \(\times\) 2270 (4.00 m\({}^{2}\)) & 2340 \(\times\) 1600 \(\times\) 2270 (3.58 m\({}^{2}\)) & \\
84A & 2400 \(\times\) 1790 \(\times\) 2270 (3.80 m\({}^{2}\)) & 2390 \(\times\) 1740 \(\times\) 2270 (3.99 m\({}^{2}\)) & \\
84B1 & 2420 \(\times\) 1600 \(\times\) 2270 (3.87 m\({}^{2}\)) & 2500 \(\times\) 1620 \(\times\) 2270 (4.06 m\({}^{2}\)) & \\
84B & 2340 \(\times\) 1590 \(\times\) 2270 (3.73 m\({}^{2}\)) & 2430 \(\times\) 1650 \(\times\) 2270 (4.01 m\({}^{2}\)) & \\
84C & 2180 \(\times\) 1740 \(\times\) 2270 (3.79 m\({}^{2}\)) & 2340 \(\times\) 1620 \(\times\) 2270 (3.80 m\({}^{2}\)) & \\
84D & 2340 \(\times\) 1790 \(\times\) 2270 (3.72 m\({}^{2}\)) & 2340 \(\times\) 1790 \(\times\) 2270 (4.05 m\({}^{2}\)) & \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Dimensions and construction methods for the bathrooms in each housing unit. Figure 2: Cross-sections of bathrooms for which the (a) UBR system and (b) wet construction method had been applied. located at the center position of each bathroom with a height of 1.2 m. One NA-28 was also located 1 m from the door. In total, eight microphones were used simultaneously for the noise-level measurements for 11 housings with different floor plans, while only one NA-28 was installed in the bathroom of the lower floor for the remaining properties (\(N\) = 53). Figure 3 shows the experimental setup for the measurements in the bathroom and adjacent rooms of the lower floor. The views of the experimental setups in the bathroom and living room are also shown in Figure 4.  
The water supply and drainage noises were generated by three consecutive operations of each sanitary ware including the water closet, basin, and bathtub. After the bathtub and basin were filled full of water, the water was drained through the pipe.