In this paper, the measurements of underwater noise generated from impact pile driving during the construction of offshore wind farm in the southwest coast of Korea were carried out to investigate the acoustic characteristics and to estimate the sound pressure level for the range. 622 snapshot of the noise measured at about 665 m from the beginning to the end of a single piling show a small variation of sound exposure level as well as peak sound pressure level and the average spectrum of that is highly correlated to the length and sound speed of the pile. The noise levels measured as a function of range were compared with the predictions obtained from the both numerical wave propagation model and empirical model. The wave propagation modeling was conducted using the broadband application of range dependent acoustic model (RAM) based on parabolic equation for the concept of multiple point sources. The damped cylindrical spreading model (DCSM) including the decay factor composed of water depth, reflection coefficient between the water and sediment and launch angle to the bottom was used for the empirical model. The measured noise levels are in good agreement with the modeling results. The source level of pile driving noise and the relationship between the sound exposure level and peak sound pressure level were discussed and the model is further applied to predict the noise contours at the construction area.