The effect of pile driving noise on the marine environment is an important factor in environmental impact assessment of planned marine structures, such as ports, bridges or offshore wind farms. Models for predicting the noise levels are essential in order to successfully predict and control the environmental impact of noise produced by such activities in the planning phase. The first COMPILE workshop was organized in 2014 by the Hamburg University of Technology and TNO to allow a cost efficient validation of different numerical models for underwater pile driving noise that have been developed by various institutes around the world. This workshop involved the prediction of relevant acoustic quantities at different ranges and depths for a generic pile-driving set-up, and allowed the results of different models to be compared. Subsequently, the COMPILE II workshop was held in November 2017. The benchmark case for this workshop was set up by TUHH, TNO and E.ON Climate & Renewables and is based on a real-life example, allowing for a model validation based on measurements. The model parameters for the pile and the environmental conditions will be described, and a selection of the outcomes of the workshop will be presented. Copyright © by International Institute of Acoustics & Vibration. All rights reserved.