## 3 Results
### Intelligibility  
For the measurement of intelligibility, indoor noise was the same as the conditions for turning off air-conditioning in Section 3.2. Usually, the values of STI are evaluated as \"bad\", \"poor\", \"fair\", \"good\", or \"excellent\" using IEC 60268-16 [8], hereafter referred to as the IEC SCALE. In this study, the IEC SCALE is applied to the measured RASTI to evaluate the speech transmission performance of the room with respect to the intelligibility.  
In the case of sound source S1, which assumes listening in the lobby during a conversation, the values of RASTI are 0.59-0.72, and the average is 0.64; thus, the lobby is mostly evaluated as \"good\" on the IEC SCALE. The values of RASTI of the entrance hall are 0.48-0.66, and the average is 0.59, which is generally evaluated as \"fair\" on the IEC SCALE, meaning the area's intelligibility is inferior to that of the lobby. In the mezzanine, although the measuring sample is small, the values of RASTI are 0.59-0.68, which can be evaluated as \"good\" or \"fair\". For sound source S2, which assumes listening in the lobby to speech from the entrance hall, the values of RASTI are 0.52-0.61, and the average is 0.56, which is evaluated to be approximately \"fair\" using the IEC SCALE. This is similar to the aforementioned results of the entrance hall for lobby speech. The trend of easy conversations in the same room but poor-quality sound between different rooms supports the reputation of the sound environment of the lobby.  
Here, we confirm the relationship with the distraction distance \(r_{d}\)[11], which is an index for an open office where speech transmission performance is important. The relationship between the distance from the sound source and the value of RASTI is shown in Figure 9. It can be seen that RASTI declines as the distance from the sound source increases for both sound sources. Since \(r_{d}\) is the distance from the speaker when STI < 0.5, all the results in this study are distractions. However, when there is a sound source in one room, the RASTI in the other room is about 0.5-0.6, which is close to the boundary value of \(r_{d}\). This measurement was performed with the air-conditioning off and no guests present. The indoor noise at the time was 37-38 dB, as shown in Section 3.2, but the indoor noise during usual hotel operations is about 50 dB, as shown in Section 3.1. Thus, since the actual background noise is  
Figure 8: Frequency characteristic of the sound pressure level of indoor noise in (**a**) the lobby, (**b**) entrance hall, and (**c**) mezzanine. AC means air-conditioning.  
more than 10 dB higher than that at the time of the measurement, the actual values of RASTI may be of poorer quality than these results.  
Figure 10 shows the distributions of the values of RASTI. The RASTI at sound source S1 is shown in Figure 2(a), and was assumed from the maximum value of the adjacent measurement point. Focusing on the relationship between sound source S1 and measurement point D6 shows that RASTI has its minimum value here. A hexagonal water board is present in the entrance hall, and a pillar is located between the lobby and the entrance hall, both of which are in a straight line between sound source S1 and measurement point D6. For sound source S2, the rows of pillars have a similar relationship. It is inferred that these architectural objects became acoustic obstacles and produced the notable changes in intelligibility between the lobby and the entrance hall for reasons other than distance.  
Figure 10: Distribution of intelligibility in the room: (**a**) assuming an utterance in the lobby and (**b**) assuming an utterance in the entrance hall.  
Figure 9: Relationship between the distance from the sound source and the value of RASTI: (**a**) sound source S1 and (**b**) sound source S2.