The ability for marine species to detect and thereby avoid potentially harmful collision with the moving parts of a tidal stream turbine depends on relative levels of the ambient sound with the acoustic emissions from the turbine. Tidal streams targeted for exploitation by renewable energy converters are by their nature highly energetic environments often with high ambient sound levels. Commonly the first time that the operational sound from new tidal turbines can be measured is after it has been installed and is already interacting with animals in the marine environment. A modelling solution is therefore required to estimate whether marine animal will be able to hear and avoid contact with turbines. An acoustic-structural interaction model is used to calculate the acoustic output of tidal turbines. The cumulative sound of an array of tidal turbines and its dependence on bathymetry is calculated using a parabolic equation code. Modelled and measured sound pressure levels give information on potential upstream warning distances/times for animals which help us consider collision risk.