From accessible musical instrument plates characterization towards an analysis framework for the conservation of historical musical instruments.

Over the past decades, research on the vibroacoustic analysis and modeling of musical instruments has gained increasing attention. Within the framework of the NEMUS project, this thesis focuses on the experimental vibroacoustics analysis of musical instruments plates. Specifically, this research aims to validate experimental protocols and techniques for characterizing the mechanical and material properties of string-based musical instrument soundboards, which play a crucial role in efficiently radiating sound generated by the strings. An inverse parameter estimation method is introduced to enable the characterization of the elastic constants of instrument plates. This approach supports the development of physics-based models within the NEMUS project and offers a practical tool for luthiers and restorers to obtain accurate material property data. The methodology is complemented by the validation of a more accessible experimental modal analysis ecosystem, designed to facilitate the acquisition of modal properties via a cost-effective approach. Several application scenarios are presented to demonstrate the accuracy and reliability of the proposed analysis methods. Two case studies illustrate the application of these techniques and address the uncertainties involved in estimating the elastic features of string-based musical instruments. A non-dimensional numerical modal analysis framework based on the Finite Element Method is developed, highlighting the limitations of conventional assumptions typically adopted in the modeling orthotropic plates. Finally, the thesis explores the impact of uncertainty in material characterization through a pilot study on an ancient Arpicordo in non-playable condition. The results show how different characterization approaches influence the structural robustness of the instrument under static loading conditions, as assessed through numerical modeling. The study ultimately advocates for the integration of uncertainty and robustness analyses within a comprehensive reverse engineering protocol, supporting restorers and instrument makers in making informed decisions when dealing with these fragile and historically valuable structures.