Underwater noise generated by impact pile driving has potentially harmful effects on aquatic animals and their environment. In effort to predict sound radiation from piling activities, a structural acoustics finite-difference, time-domain (FDTD) model has been developed for transient analysis of a partially submerged cylindrical pile. Three coupled partial differential equations govern vibration of the pile wall and six partial differential equations govern its boundary conditions. The space-time gridding underlying the numerical computations controls selection of an appropriate time step while the physical geometry of the pile imposes an upper limit on the frequency bandwidth of wall oscillations and radiated sound. This bandwidth is inversely proportional to diameter for a cylindrical steel pile. The higher the frequency content in the dynamic response, the smaller the time step required in a transient analysis. So as diameter of the pile decreases, smaller time steps are required to capture the total bandwidth observed in field data. Results of correlations between radiated sound predicted by the FDTD model and acoustic field data from piles of different diameter are presented. [Work supported by the Georgia Institute of Technology and Oregon Department of Transportation through a subcontract from Portland State University.]