## 3 Results
### Automatic Bowel Sound Detection  
Table 1 lists the number and length of BS and non-BS segments obtained at each SNR threshold used in the STE method. Table 1 reveals the following pattern for both cases (before and after consumption of carbonated water by participants): As the SNR threshold decreases, the numbers of both BS and non-BS segments increase until a certain threshold, after which the numbers of segments decrease. Additionally, the values in the table confirm that the lengths of both segments also increase with decrease in SNR. The values of length and number of both segments were larger after consumption of carbonated water than those before consumption, and BS segments were longer than non-BS segments. To evaluate the automatic extraction performance of the proposed method, the respective segments were divided in a ratio of 3:1 for training data and testing data. Tables 2 and 3, respectively, present the results of 100 ANN-based approach trials that used MFCC and PNCC as acoustic features to derive the average classification accuracy. Table 2 reveals that for the case before consumption of carbonated water, accuracy slightly degraded with decrease in the SNR threshold, whereas the accuracy increased with decrease in SNR threshold in the case after consumption. Table 3 demonstrates that when PNCC is used, classification accuracy increases as SNR threshold decreases, for cases both before and after consumption of carbonated water. Furthermore, we can see that the highest accuracy is obtained when the SNR threshold is 0 dB. Figure 3 shows the results of a comparative analysis of extraction accuracy before and after consumption of carbonated water when using MFCC and PNCC, respectively. Table 3 shows that PNCC is more accurate than MFCC for all SNR thresholds. When the SNR threshold is 0 dB before the consumption of carbonated water, the average of PNCC becomes sufficiently larger compared to that of MFCC. In general, a BS with lower sound-pressure occurs before consumption of carbonated water than after consumption. This suggests that PNCC is effective in classifying such sounds. On the basis of the abovementioned observation, a subsequent automatic evaluation of bowel motility was conducted using PNCC with an ANN-based approach. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Threshold** \\ **of SNR (dB)** \\ \end{tabular} } & \multicolumn{4}{c}{**Before Soda Intake**} & \multicolumn{4}{c}{**After Soda Intake**} \\ \cline{2-9}  & \multicolumn{2}{c}{**No. of Segments**} & \multicolumn{2}{c}{**Length of Segments(s)**} & \multicolumn{2}{c}{**No. of Segments**} & \multicolumn{2}{c}{**Length of Segments(s)**} \\ \cline{2-9}  & **BS** & **Non-BS** & **BS** & **Non-BS** & **BS** & **Non-BS** & **BS** & **Non-BS** \\ \hline
2 & 396 & 4840 & \(0.42\pm 0.59\) & \(0.34\pm 1.49\) & 1538 & 6372 & \(0.59\pm 1.82\) & \(0.30\pm 1.15\) \\
1 & 439 & 10202 & \(0.59\pm 0.91\) & \(0.36\pm 1.28\) & 1463 & 15614 & \(0.85\pm 2.47\) & \(0.29\pm 0.82\) \\
0.5 & 441 & 13444 & \(0.90\pm 2.27\) & \(0.39\pm 1.35\) & 1378 & 21202 & \(1.23\pm 3.61\) & \(0.32\pm 0.53\) \\
0 & 409 & 14904 & \(1.51\pm 3.83\) & \(0.47\pm 1.72\) & 1264 & 23522 & \(1.86\pm 4.59\) & \(0.39\pm 0.65\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Number and length of BS and non-BS segments obtained at each SNR threshold used in the STE method.