Resonance ultrasound spectroscopy (RUS) is an experimental method by which material properties are obtained by careful observation of the resonant vibrations of a meticulously crafted sample. Among the most common applications of this technique is the determination of single-crystal elasticity. Previous works have considered the reliability of elasticity information obtained via the RUS method when the material is of isotropic or cubic symmetry, and this work extends these efforts to materials with hexagonal symmetry, such as titanium di-boride. The reliability of elasticity information obtained by RUS is evaluated by Sobol Analysis and by close examination of the stiffness-frequency functionality. Findings show that the values of off-diagonal elements of the Voigt stiffness matrix are error-prone due to insensitivity of the resonant spectrum; regression of these elementsβ values is not robust to experimental errors in measuring the resonant frequencies. Techniques based on surface acoustic wave measurements are demonstrated to be a suitable supplement to RUS for more reliable determination of the off-diagonal stiffness values, forming a complete and accurate characterization of the material elasticity
