## 5 Conclusions  
Acoustic parameter measurements were performed using three omnidirectional sources: coupled loudspeakers, dodecahedron, and cubic source. The step rotation of 15 degrees was performed to determine if the measurement results of the possible source position would differ. The standard deviations of the obtained results were analyzed to compare the performance of the coupled loudspeaker source with the commonly used omnidirectional \begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{2}{c}{**SD/JND**} & **250 Hz** & **500 Hz** & **1000 Hz** & **2000 Hz** & **4000 Hz** \\ \hline \multirow{4}{*}{\(\mathrm{SD/JND}\)} & Coupled & 0.42 & 0.63 & 0.60 & 0.88 & 2.66 \\ \cline{2-6}  & Cubic & 0.95 & 0.74 & 0.78 & 1.18 & 1.20 \\ \cline{2-6}  & Dodecahedral & 0.79 & 0.64 & 0.60 & 1.06 & 0.88 \\ \hline \multirow{4}{*}{\(\mathrm{SD/JND}\)} & Coupled & 0.07 & 0.08 & 0.22 & 0.55 & 3.24 \\ \cline{2-6}  & Cubic & 0.06 & 0.16 & 0.49 & 0.39 & 0.65 \\ \cline{2-6}  & Dodecahedral & 0.02 & 0.05 & 0.15 & 0.87 & 0.61 \\ \hline \multirow{4}{*}{\(\mathrm{SD/JND}\)} & Coupled & 0.24 & 0.30 & 0.35 & 0.54 & 1.61 \\ \cline{2-6}  & Cubic & 0.3 & 0.44 & 0.54 & 0.55 & 0.61 \\ \cline{2-6}  & Dodecahedral & 0.15 & 0.27 & 0.42 & 0.71 & 0.61 \\ \hline \multirow{4}{*}{\(\mathrm{SD/JND}\)} & Coupled & 0.55 & 0.28 & 0.38 & 0.35 & 1.25 \\ \cline{2-6}  & Cubic & 0.47 & 0.57 & 0.42 & 0.32 & 0.22 \\ \cline{2-6}  & Dodecahedral & 0.34 & 0.34 & 0.26 & 0.30 & 0.28 \\ \hline \end{tabular}
\end{table} 
Table 1: Tabular representation of SD/JND values for all measured sound sources (coupled speakers, dodecahedral sound source, cubic sound source). sources. Based on the calculated parameters EDT, T30, C80, and D50, as well as the analysis of the standard deviation divided by JND, it was found that coupled loudspeakers are highly useful in measurements within the 250-2000 Hz range. It was also demonstrated that for commonly used cubic/dodecahedron sources, significant differences occur depending on the source rotation, and using three different source positions may not be sufficient. It is important to note that in T30 measurements, all sources performed similarly, so if the analysis should be limited only to reverberation time, the influence of different sources used may be neglected. The final statement is that the coupled speakers could be a cheap and effective replacement for commercial dodecahedral sound sources in room acoustic measurements. The negative features of this solution are a limited frequency range (currently 250-2000 Hz) and relatively low overall output SPL. Reaching the desired SNR with coupled speakers may be difficult in noisy environments or large venues. Further research should explore methods to improve the omnidirectional quality of coupled loudspeakers, particularly in the 4000 Hz octave, to achieve full utility in architectural acoustics measurements. Also, possibilities for higher output SPL (higher sensitivity) should be investigated. Conceptualization, B.C. ; Methodology, B.C., M.B. and J.A.F. ; Software, M.B. and J.A.F. ; Validation, B.C. and J.A.F. ; Formal analysis, B.C. ; Investigation, M.B. and J.A.F. ; Resources, M.B. and J.A.F. ; Data curation, M.B. ; Writing--original draft, B.C., M.B. and J.A.F. ; Writing--review & editing, B.C. ; Visualization, M.B. and J.A.F. ; Supervision, B.C. ; Project administration, B.C. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. Data Availability StatementData are available upon request directly from authors. The data are not publicly available due to privacy protection and the need of control over external modification and unauthorized use. The authors declare no conflict of interest. The complete measurement results are presented to support scientific transparency and further cross-verifications. The following chapter contains the measurements for both points in all significant octave bands, presented separately for all sources (Figures A1-A8).