stress wave propagation

Hi everybody, I'm so interested in analysis of wave propagation in solid medias. and I've started by studying some books like "Ultrasonic wave propagation in solid media"(Rose). My question is about the importance of this analysis  (propagation of high frequency elastic waves) in the structures. I know that the major application is in the field of Nondestructive Testing(NDT). but I don't know if it is usefull in vibrational analysis of mechanical structures (elastic waves with frequencies around KHz or MHz). is this study important in "dynamic response analysis" of mechanical structures in some special kind of loading like impact? I'd be gratefull if you could introduce me some examples.

does anyone know any current theories on the stress wave propagation in a  complex media(such as concrete or rock).(1D sphere wave or complex)

all i see is the simulation with a complex constitutive model. but i think it`s not perfect. 

hope for your help