All objects and structures vibrate in their own specific ways, the eigenmodes. If artworks and cultural assets are excited by vibrations or shocks during transport, for instance, they respond with an excitation-specific combination of their eigenmodes. These natural oscillations therefore need to be known if the optimum vibration-reducing measures are to be developed.
The eigenmodes of an object change due to damage and restoration measures, for example, as well as varying with humidity and temperature.
Comparison of the parameters that characterize the eigenmodes (e.g. their eigenfrequencies) before and after are therefore needed when evaluating damage and restorative measures, for example.
Dr. Kracht developed a test rig specifically for investigating the natural vibration behaviour of paintings; it can help obtain a clear picture of damage, even when that damage is invisible. Read more in the article “Beckmann's Carnival in motion”.