# Measurements of Room Acoustic and Thermo-Hygrometric Parameters--A Case Study +
## 4 Discussion  
This section discusses the results of the acoustic parameter measurements and statistical analysis of the data.  
The sole independent parameter was air velocity, which was purposely manipulated. The airflow rate had a significant impact on the room's air temperature and humidity. The room acoustic characteristics were also susceptible to variations in air velocity, and as was already indicated, D\({}_{50}\) in particular exhibited more significant fluctuations than did the other major acoustic parameters. When the ventilation system was turned off, it was clear that the fluctuations in acoustic characteristics were reduced or even became constant.  
Figure 11: Temperature as independent variable: a scatterplot of positive linear correlation, T\({}_{30}\) at 125 Hz (**a**), a scatterplot of negative linear correlation, C\({}_{50}\) at 125 Hz (**b**), a scatterplot of non-linear correlation, LE at 250 Hz (**c**).  
Fluctuation in air velocity was the most important environmental component affecting how the room's acoustic characteristics varied within the boundaries of this study.  
EDT and G exhibited the strongest linear relationships with temperature out of the nine acoustic parameters. At low and mid frequencies, D50 was most affected by temperature compared with the other parameters, followed by C80 and C50. Temperature had the greatest impact on G at high frequencies, followed by D50. The remaining seven parameters were all affected to a lesser extent.  
All the acoustic parameters with the exception of T30 had a distinct linear relationship with humidity. Similar to temperature, variations in humidity had a greater impact on D50 at low and mid frequencies than they did on other parameters. Among the higher bands, D50 was still the most impacted by humidity fluctuations, followed by G. Across the entire frequency range, variations in humidity had a negligible impact on LE and LF.  
In contrast to the ISO 9613-1 [17] standard, the experimental results show that sound attenuation is not sensitive to variations in humidity. The boundaries of the enclosed indoor environment and the more complicated external air medium may be accountable for this. Additionally, the current findings contradict those of [PERSON] et al. [16]. The reverberation time showed a negative linear correlation with temperature in the higher frequency bands. Moreover, it was discovered during testing that when the binary regression analysis was carried out, the results remained consistent with the one-dimensional regression analysis. The explanation for this contrary outcome could be that the study by [PERSON] et al. concentrated on underground spaces such as metro stations, which are quite vast and can be associated with strong wind speeds due to trains passing them. Furthermore, the parameter chosen was T40, which differed from the normal selection (T60, T30, and T20), and the frequency analysed exceeded 8000 Hz.  
Cross-validated RMSE and MAE were used to evaluate the model's predictability. When temperature was used as the independent variable, the model's predictions for T30 and EDT were more accurate at high frequencies. The model provided higher prediction accuracy at lower frequencies for G, C50, C80, D50, and IACC. For LE and LF, the predictions of the model were closer to the true values at mid frequencies. The results were similar when humidity was considered as an independent variable.  
It should also be noted that when rooms are too high, differences in room air temperature distribution can readily occur, which can be worsened if their ventilation system is not appropriately constructed. The resulting temperature gradient and the ensuing convective airflow have a significant impact on acoustic characteristics. This impact should be considered in the acoustic design of concert halls and theatres, where temperature fluctuations can result in distinct seating regions for the listening experience as well as the thermal expansion of metal instruments, which can cause them to become out of tune.