A minor correction: he says that the material has a resonant frequency, but in fact both material properties (mostly Young’s modulus and density) and object’s shape define it’s resonant frequencies. Material itself doesn’t have resonant frequency.
The resonant frequencies can be easily computed using Finite Element modeling software, such as open source Salome-Meca & Code Aster using Modal Analysis. The result is frequencies and animations for each vibration mode - they can be quite interesting, like for example various torsional modes.
