# Speech Intelligibility Analysis and Approximation to Room Parameters through the Internet of Things
## 3 Results
### Study of the Application of the SII Measurement System in a Room  
Once the RT60, C50, C80 and STI parameters are determined in the evaluating room, we have applied the intelligibility analysis in different positions in a classroom to plot SII maps according to the position where the hearer is located and therefore, be able to estimate which locations have the worst perception for speech. A representation system has been developed that reproduces in 2D and 3D the dimensions of the room to be treated, as well as the calculated values of SII for the indicated positions of each node. The system has been prepared to overprint a plan of the room if available to facilitate the analysis of the results. Figure 7 shows two 3D models (out-of-scale) with a SII study in 2.1.1 and 1.0.1 classrooms at the ETSE of the University of Valencia. The dimensions of these rooms are \(8\times 12\times 3\) and \(8\times 26\times 3\) meters, respectively. In Figure 8, two heat-map-like (out-of-scale) representations of the SII can be seen, allowing us to graphically assess speaker distances and positions from which there may be intelligibility problems. Since the SII measurements are asynchronous, we can place the 4 receiver nodes of our system in as many positions as we wish and take numerous samples of the intelligibility by executing the code multiple times. In Figure 7a, we can see the 16 positions where the measurements have been performed with the obtained SII values. On the other hand, in Figure 7b, we can see that 14 measurements have been taken, demonstrating the flexibility of the system when taking SII samples. In Figure 8, we can see 2 SII representations of the same classrooms (2.1.1 and 1.0.1) in the form of a heat-map, which allows a draft of the speech intelligibility in the room, at a glance. The more samples we take, the more accurately we will generate the heat-maps shown in Figure 8.  
Figure 6: 18-band spectrum needed for SII computation for: (**a**) excellent intelligibility and (**b**) bad intelligibility. Equivalent hearing threshold levels \(T_{i}\) for normal speech as the overlapping line (red). The values obtained represent accurately the perception of speech in the rooms studied. In the case of classroom 2.1.1, we have placed the node that simulates the speaker in the position of the teacher's table, as we can see in Figures 7a and 8a, since this is the most common place in this classroom. From the first rows with maximum SII values of 0.9 we see how the SII values decrease until the minimum of 0.61 in the last positions studied. The heat-map in Figure 8a helps us to see more easily how this drop in SII has a diagonal pattern from the speaker position to the opposite corner of the classroom. The analysis of SII in classroom 1.0.1, shown in Figures 7b and 8b, has been performed by placing the emitter node in a central position with respect to the transverse axis of the classroom, because in this classroom it is common for the speaker to be located in this area. In Figure 7b we can see that the maximum values of SII are 0.93 while the minimum is 0.54. The values in the areas farther away from the speaker are now lower than in the previous case, a fact that is more easily observed in Figure 8b where darker shades of blue are visible in the background of the classroom. However, as class 1.0.1 is more than twice the size of class 2.1.1, SII would be even lower. We have found the explanation in the reverberation that reinforces the acoustic signals from the emitter and allows the SPL levels to not drop as much towards the end of the classroom as would be expected. Specifically, RT60 measured in classroom 2.1.1 is 0.58 s while RT60 in classroom 1.0.1 is  
Figure 8: Heat-maps of SII measurement mappings in different rooms at the ETSE ((**a**). Classroom 2.1.1 and (**b**). Classroom 1.0.1). Marked position of sound source node (blue cicle). Figure 7: 3D models and SII measurement mappings in different rooms at the ETSE ((**a**). Classroom 2.1.1 and (**b**). Classroom 1.0.1).