## 4 Discussion and Conclusions  
This study proposes a system for automatic evaluation of bowel motility on the basis of acoustic features in BS time domains obtained by automatically extracting BS from sound data recorded using a noncontact microphone. Although studies related to bowel motility using BS have been conducted previously [2; 3; 4; 5; 6; 7], those studies used electronic stethoscopes that were applied to the surface of the body. Our recent research has demonstrated that bowel motility can be evaluated from sound data \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Threshold of SNR (dB)**} & \multicolumn{5}{c}{**PNCC**} \\  & \multicolumn{5}{c}{**Before Soda Intake**} \\ \cline{2-6}  & **Sen (\%)** & **Spe (\%)** & **PPV (\%)** & **NPV (\%)** & **Acc (\%)** \\ \hline
2 & 71.5 \(\pm\) 23.1 & 85.0 \(\pm\) 12.0 & 25.5 \(\pm\) 21.5 & 96.5 \(\pm\) 6.6 & 85.5 \(\pm\) 9.6 \\
1 & 75.2 \(\pm\) 23.8 & 88.8 \(\pm\) 8.0 & 17.6 \(\pm\) 15.1 & 98.8 \(\pm\) 2.0 & 88.7 \(\pm\) 7.3 \\
0.5 & 74.1 \(\pm\) 23.5 & 90.2 \(\pm\) 5.8 & 15.4 \(\pm\) 13.7 & 99.2 \(\pm\) 1.0 & 90.0 \(\pm\) 5.5 \\
0 & 72.4 \(\pm\) 23.0 & 90.4 \(\pm\) 6.4 & 15.2 \(\pm\) 13.5 & 99.4 \(\pm\) 0.8 & 90.2 \(\pm\) 6.3 \\ \hline \hline \multirow{2}{*}{**Threshold of SNR (dB)**} & \multicolumn{5}{c}{**PNCC**} \\  & \multicolumn{5}{c}{**After Soda Intake**} \\ \cline{2-6}  & **Sen (\%)** & **Spe (\%)** & **PPV (\%)** & **NPV (\%)** & **Acc (\%)** \\ \hline
2 & 78.6 \(\pm\) 8.1 & 85.2 \(\pm\) 6.0 & 54.7 \(\pm\) 12.8 & 94.4 \(\pm\) 2.8 & 84.4 \(\pm\) 4.1 \\
1 & 82.9 \(\pm\) 8.7 & 88.6 \(\pm\) 5.3 & 40.0 \(\pm\) 12.9 & 98.2 \(\pm\) 1.1 & 88.3 \(\pm\) 4.7 \\
0.5 & 85.4 \(\pm\) 7.2 & 90.1 \(\pm\) 3.4 & 34.5 \(\pm\) 12.9 & 98.9 \(\pm\) 0.7 & 89.9 \(\pm\) 3.1 \\
0 & 84.4 \(\pm\) 8.7 & 90.0 \(\pm\) 3.6 & 30.7 \(\pm\) 12.8 & 99.1 \(\pm\) 0.7 & 89.8 \(\pm\) 3.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Results of automatic BS extraction using an ANN-based approach based on PNCC (using performance evaluation through leave-one-out cross validation). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Threshold of SNR (dB)**} & \multicolumn{2}{c}{**BS Detected/min.**} & \multicolumn{2}{c}{**SNR (dB)**} \\ \cline{2-6}  & **Before Soda Intake** & **After Sofa Intake** & **_P Value** & **Before Soda Intake** & **After Sofa Intake** & **_P Value** \\ \hline
2 & 3.97 \(\pm\) 3.62 & 6.97 \(\pm\) 3.83 & \textgreater{}0.001 * & 5.38 \(\pm\) 0.88 & 6.20 \(\pm\) 0.64 & 0.007 * \\
1 & 6.59 \(\pm\) 4.70 & 9.54 \(\pm\) 4.28 & 0.015 * & 3.83 \(\pm\) 0.77 & 4.65 \(\pm\) 0.56 & 0.002 * \\
0.5 & 7.79 \(\pm\) 5.48 & 10.69 \(\pm\) 3.82 & 0.008 * & 3.05 \(\pm\) 0.82 & 3.86 \(\pm\) 0.56 & 0.002 * \\
0 & 7.90 \(\pm\) 5.35 & 11.18 \(\pm\) 3.70 & 0.014 * & 2.44 \(\pm\) 0.94 & 3.06 \(\pm\) 0.54 & 0.036 * \\ \hline \hline \multirow{2}{*}{**Threshold of SNR (dB)**} & \multicolumn{2}{c}{**Length of BS(s)**} & \multicolumn{2}{c}{**SS Interval(s)**} \\ \cline{2-6}  & **Before Soda Intake** & **After Sofa Intake** & **_P Value** & **Before Soda Intake** & **After Sofa Intake** & **_P Value** \\ \hline
2 & 0.56 \(\pm\) 0.46 & 0.52 \(\pm\) 0.15 & 0.126 * & 23.32 \(\pm\) 17.38 & 10.26 \(\pm\) 5.66 & 0.001 * \\
1 & 0.85 \(\pm\) 0.80 & 0.67 \(\pm\) 0.20 & 0.457 * & 12.59 \(\pm\) 10.11 & 6.84 \(\pm\) 3.55 & 0.013 * \\
0.5 & 1.20 \(\pm\) 1.30 & 0.98 \(\pm\) 0.45 & 0.323 & 9.83 \(\pm\) 8.25 & 5.37 \(\pm\) 2.51 & 0.014 * \\
0 & 1.89 \(\pm\) 2.55 & 1.30 \(\pm\) 0.61 & 0.379 & 9.54 \(\pm\) 7.94 & 4.74 \(\pm\) 2.57 & 0.021 * \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Results of automatic bowel motility evaluation using acoustic features in four time domains: BS detected/min, SNR (dB), length of BS (s), and SS interval (s). recorded using a noncontact microphone the same way as it can be evaluated using data recorded with a stethoscope [8]. However, the extraction of BS from sound data performed in this study was based on manual labeling.