Obtaining a Scaled Modal Model of Panel Type Structures Using Acoustic Exciation, #128

For a modal analysis, in general, a structural excitation is used. This means : performing a hammer excitation or attaching shakers to the structure. One of the typical problems with shaker excitation, especially for light-weight components, is that its dynamic characteristics, the effect of the attachment (additional mass and rotational stiffness), can have a disturbing effect on the measured modal characteristics. In this paper, it will be shown that an accurate modal model can be extracted from measurements of an acousticcon tactlessexcitation. The conclusion that eigenfrequencies, modeshapes and damping can be found correctly, can be taken from a comparison with a finite element model. A typical problem of acoustic excitation is to obtain the correct scaling of the modes. A method is proposed to calculate accurately the modal mass from this kind of excitation. This means that the whole model can be known and transfer functions with non-measured structural DOFs as input can be correctly synthesized. This shows that acoustic excitation can be a useful tool when one wants to minimize the disturbing effect of the shakers attachment and still wants an accurate model.