Animal-borne tags provide insights into the acoustic communication of southern right whales (Eubalaena australis) on the calving grounds

No abstract

Sound mapping over large areas can be computationally expensive because of the large number of sources and large source-receiver separations involved. In order to facilitate computation, a simplifying assumption sometimes made is to neglect the sound speed gradient in shallow water. The accuracy of this assumption is investigated for ship generated sound in the Dutch North Sea, for realistic ship and wind distributions. Sound maps are generated for zero, negative and positive gradients for selected frequency bands (56 Hz to 3.6 kHz). The effect of sound speed profile for the decidecade centred at 125 Hz is less than 1.7 dB.

An analysis is presented of sound measurements performed near two detonations of unexploded ordnance (UXO) in the North Sea, at distances ranging from 1.5 to 12 km. The charge masses of the detonations were 325 and 140 kg TNT equivalent. The objective of the measurements was to improve the accuracy of model predictions of the area where UXO detonations affect harbour porpoises in the North Sea. For the predictions, an explosion emission model is combined with a shallow-water propagation model. The prediction model was previously validated for distances up to 2 km. The measurements reported here allowed validation up to a distance of 12 km. The measured levels and spectra are well explained by the model calculations. The model results depend strongly on the sea sediment layering. The propagation of high-frequency components appears to be affected primarily by the silty top layer, while low-frequency components are affected also by deeper sandy layers. Measured and calculated noise levels are used to determine permanent-threshold-shift effect distances for harbour porpoises (Phocoena phocoena). Values ranging from 2 to 6 km are found for the two detonations.

From studies into marine biology, it is known that the behavior of marine mammals and fish can be influenced by the ambient underwater sound level. In busy seas like the North Sea in Europe, sound from shipping traffic is largely responsible for the low frequency part of the ambient sound. In this work, possibilities to regulate the underwater radiated sound of ship traffic are investigated. This involves measures that look at traffic flows and operational use of the vessels, to determine what can be done to reduce the shipping sound levels in certain marine areas. Three types of operational measures are considered: (1) the effect of spatial planning (for example, changing the location of shipping routes), (2) the introduction of a radiated sound limit for vessels in a certain area, and (3) the introduction of a speed limit for vessels in a certain area. The proposed measures have been analyzed on their effect and effectiveness, by means of numerical analysis. Calculations have been performed for a generic ship traffic flow, based on actual recorded AIS data from a North Sea shipping lane, using a speed depended model for the source level of different ship types and a sound propagation model.