From the knowledge of piezoelectric material tensorial components and using the finite-element method, it is possible to calculate the electrical impedance vs. frequency and simulate the mechanical deformation of piezoelectric bars. To check the validity of the simulation, interferrometric measurements of the mechanical deformation amplitude were performed. It is shown that these measurements can reveal the homogeneity of the materials under study and that a small error in the tensorial parameter absolute values leads to an inconsistent picture of simulated mechanical deformation.