The contribution of shipping sound to the dutch underwater soundscape: Past, present, future

Understanding the influence of changes in shipping intensity on the temporal and spatial distribution of underwater sound is needed for marine spatial planning. We introduce a practical approach for the estimation of underwater shipping sound for both past and future. Shipping sound has been identified as one of the largest contributors to the Dutch North Sea soundscape at frequencies below 10 kHz. We have estimated sound pressure levels and total acoustic energy from shipping for the years 1948 to 2035. There was a doubling in terms of energy between 1965 and 2000, from 650 joules to 1300 joules. The expected increase, if the source levels remain constant, is around 1000 joules from 2000 to 2020 and another 15 % rise, of the total acoustic energy, until 2036. This energy could be decreased by: relocation of shipping routes, speed limits, and more silent ships in the future. As an example, sound maps are calculated for ICES 209 research vessels to provide an insight into a possible way to decrease the shipping sound in the Dutch North Sea.