The construction of offshore wind-farms generates a range of high-level underwater noise to which marine mammals, which have acute underwater hearing and use acoustics as their primary sensory modality, is at levels that could cause hearing or physical damage. Risks will rise as pile diameter increases. We explore the risks posed by pile driving to the hearing of marine mammals found in the vicinity of the UK offshore wind farms using a cumulative exposure model incorporation animal movement and simple propagation models. Runs of these models showed that marine mammals’ hearing could be affected at ranges of several kms and highlight animal movement and sound propagation as poorly measured parameters with a major influence on the risk of damage.