4. Modal testing

The modal testing stage consists of estimating a set of FRF of the structure by applying well-chosen dynamic forces and measuring its vibratory responses. The number of points at which the forces are applied and the responses measured can vary from 1 to several dozen, or even several hundred (particularly for measurements carried out using a scanning laser vibrometer).

Test quality directly affects the credibility of modal identification results, so it's essential to design and implement modal tests with the utmost care.