**4. Discussion and Conclusions**

The numerical studies carried out by the authors concerned dynamic responses of simple one-dimensional structures. The analysed responses covered natural frequencies and modes of natural vibrations, and the accuracy of their representations. The study aimed at the investigation of the influence of this accuracy on wave propagation responses in two one-dimensional structures, those being: a rod modelled according to the elementary theory of rods and a beam modelled according to the elementary theory of beams. Despite the fact that those structural elements are one-dimensional and the employed theories of their dynamic behaviour are the simplest available, the conclusions presented below remain valid for other structural elements. They also apply to two and three-dimensional structural elements of complex geometries and material properties as long as their numerical representations have the features typical of periodic structures, i.e., characterised by a large number of finite elements of the same or similar size, which is a typical for wave propagation analysis.

The conclusions based on the results obtained by the authors and presented in the current work can be summarised in the following way:


**Author Contributions:** Concept, methodology, validation, formal analysis, investigation, resources, data analysis, writing—original draft preparation, M.P.; writing—review and editing, A.Z.; visualisation, M.P.; supervision, A. ˙ Z., ˙ M.K., and M.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** The authors would like to gratefully acknowledge the support of the Academic Computer Centre in Gda ´nsk, the provider of the software used for the research done by the author and described in this paper.

**Conflicts of Interest:** The authors declare no conflict of interest.
