The excitation levels for modal testing are usually reasonably low. There is no need to provide large force levels for conducting a modal test especially if appropriate response transducers (ac- celerometers) are selected with good sensitivity and resolution, as well as high quality, high resolution (24-bit technology is fairly standard in today’s commercial offerings) data acquisition systems. The level only needs to be sufficient enough to make good measure- ments. In fact, larger force levels tend to overdrive the structure, exciting nonlinear characteristics of the structure and providing poorer overall measurements than with lower level force tests. For this reason, again, on larger structures, it is often desirable to use multiple shakers at lower force levels to more evenly distribute force than a few single shakers operating at high level forces.