## 6 Discussion  
The aforementioned \"feeling of silence\" and \"feeling of serenity\" were clearly affected by the absorption coefficients of the room. However, the \"feeling of silence\" is commonly known to be influenced by the absolute sound pressure level as well. In this section, we discuss the relationship between the \"feeling of silence\" and background noise level. We measured not only the reverberation time but also the sound pressure levels of each absorption pattern at the point marked positions, as shown in Figure 15. Then, the exposed fan noise level was increased to 67 dB from the subjective test setting to improve the signal-to-noise ratio. The measurement results of column \"d\" are shown in Figures 16 and 17. Figure 16 shows the results of the A-weighted values, and Figure 17 shows those of the 1 kHz octave-band values. The sound pressure levels decreased from the boundary position \"d6\". The amount of decrease differed for each absorption condition. The larger the absorption area, the larger the decrease in the value. The A-weighted values at \"d1\" and \"d2\" were larger than that at \"d3\". The rising levels at low-frequency bands could be considered because the receiving positions were near the forward wall. Using these results, the correlation coefficients between the sound pressure levels at position \"d3\", around the center of the room, and the psychological scale values of each subjective item in Section 2 were calculated. Table 10 lists the results of these calculations. The items \"feeling of silence\", \"feeling of serenity\", \"sense of quality\", and \"user preference\" had strong negative correlation with sound pressure levels. \"Feeling of silence\" and \"feeling of serenity\" were found to be related to the absorption coefficient of the room from the subjective tests in Sections 2-5. However, these subjective items were also related to the absolute sound pressure levels of the room used in the subjective evaluation. From these discussions, we could not identify whether the dominant factor was the \"absorption coefficient of the room\" or the \"absolute sound pressure level\". Figure 16: Results of the A-weighted sound pressure level on line “d” on each absorption pattern. The dotted line represents the boundary of the front room and evaluation space. Figure 15: One evaluation space is used for sound-pressure-level measurement. The levels were obtained at dot positions on each absorption pattern (A–E shown in Figure 4). We also measured background noise levels in nine rooms in modern Japanese dwellings, as described in Sections 4 and 5. Table 11 presents the measurement results. All rooms had A-weighted levels of less than 45 dB. Table 12 shows the correlation coefficients between the background noise levels and psychological scale values. Compared to the results in Table 9, the coefficients of all items were low in every octave band and A-weighted levels in Table 12. The coefficient values of \"feeling of silence\" and \"feeling of serenity\" were also under 0.6. From these calculations, the background noise level could not be directly associated with the \"Feeling of silence\" and \"Feeling of serenity\" in dwellings. \begin{table}
\begin{tabular}{c c c} \hline
**Item** & **A-Weighted** & **1000 Hz** \\ \hline Reverberance & 0.94 ** & 0.93 ** \\ Feeling of silence & \(-\)0.95 ** & \(-\)0.97 ** \\ Feeling of serenity & \(-\)0.94 ** & \(-\)0.93 ** \\ Sense of room volume & 0.43 & 0.36 \\ Feeling of oppression & \(-\)0.54 & \(-\)0.57 \\ Sense of quality & \(-\)0.92 ** & \(-\)0.93 ** \\ User preference & \(-\)0.90 ** & \(-\)0.88 ** \\ \hline \end{tabular}
\end{table} 
Table 10: Correlation coefficients between the sound pressure levels at position “d3” in the evaluation space and psychological value of each evaluation item. Figure 17: Results of the 1-kHz octave-band sound pressure level on line “d” in each absorption pattern. The dotted line represents the boundary between the front room and evaluation space.