Predicting effects of underwater pile driving on marine life requires coupling of pile source models with biological receiver models. Fishes in particular are very vulnerable to tissue damage and hearing loss from pile driving activities, especially since they are often restricted to specific habitat sites and migratory routes. Cumulative sound exposure level is the metric used by government agencies for sound exposure criteria to protect marine animals. In recent laboratory studies, physical injury and hearing loss in fish from simulated impact pile driving signals have even been correlated with this metric. Mechanisms for injury and hearing loss in fishes, however, depend on relative acoustic particle motion within the body of the animal, which can be disproportionately large in the vicinity of a pile. Modeling results will be presented showing correlation of auditory tissue damage in three species of fish with relative particle motion that can be generated 10–20 m from driving a 24-in diameter steel pile with an impact hammer. Comparative results with vibratory piling based on measured waveforms indicate that particle motion mechanisms may provide an explanation why the very large cumulative sound exposure levels associated with vibratory pile driving do not produce tissue damage.