Ship source strength estimation in shallow water

Abstract

Continuous underwater noise from commercial ship traffic is an important pressure on the marine environment that has to be taken into account as stated in the Marine Strategy Framework Directive adopted in the EU. Monitoring of the underwater ambient noise level has been performed in the frame of the Life+ BIAS project together with underwater noise propagation modelling resulting in noise maps. In order to improve the modelling of anthropogenic noise based on AIS traffic data, it is essential to provide better source level (SL) input for individual ships. The SL can be obtained using the data from the underwater noise monitoring. Long-term recordings provide information about ships’ multiple passages. In shallow water, sound prop-agation modelling should be applied for accurate loss estimation. If the modelling is performed for some particular frequency bands, estimation of the loss needs even more calculation effort. This paper proposes a simplified approach for more efficient calculation of the losses. The calculated results are compared with the measurements in different geographical positions and sea conditions. The topic of ship source directionality is addressed. The repeatability of the results is checked for the different passages of the same ship during the year.Continuous underwater noise from commercial ship traffic is an important pressure on the marine environment that has to be taken into account as stated in the Marine Strategy Framework Directive adopted in the EU. Monitoring of the underwater ambient noise level has been performed in the frame of the Life+ BIAS project together with underwater noise propagation modelling resulting in noise maps. In order to improve the modelling of anthropogenic noise based on AIS traffic data, it is essential to provide better source level (SL) input for individual ships. The SL can be obtained using the data from the underwater noise monitoring. Long-term recordings provide information about ships’ multiple passages. In shallow water, sound prop-agation modelling should be applied for accurate loss estimation. If the modelling is performed for some particular frequency bands, estimation of the loss needs even more calculation effort. This paper proposes a simplified approach for more efficient calculation of the losses....