Method for the simplistic modelling of the acoustic footprint of the vessels in the shallow marine area

Abstract

The definitions of the 11th descriptor of the EU Marine Strategy Framework Directive (MSFD) “Underwater noise and other forms of energy” outlines the standards for the continuous noise evaluation and monitoring in the European seas. Long lasting fluctuations of the continuous underwater noise at the shallow marine areas in the low frequency bands (<1 kHz) are mostly associated with the shipping noise, where these fluctuations are sensitive to changes in the spatial distribution of human activities, or changes of environmental and climatic variables. Underwater noise modelling is usually considered as a supplement to noise measurements, where models increases the utility of the measurement results. Noise mapping is considered as a form of spatial modelling, providing a convenient and accessible way to visualise models. Therefore, underwater noise models and maps can be used in management and evaluation of environmental state. There are number of freely available widely used noise source and sound propagation models. Still the simplistic logarithmic rules purposed for the sound propagation loss computations do not account for the number of factors in the marine environment, i.e. sediment type, water depth or frequency. On the other hand the sophisticated physical models purposed for the description of the footprint of noise sources such as ships are complex and their programing requires very specific knowledge. In this paper the details of the method purposed for modelling of the ship noise footprint in shallow seas is presented. Proposed method allows to compute: • depth dependent ship sound transmission losses in 1 Hz frequency bands; • sound propagation losses during different seasons (summer/winter); • acoustic footprint accounting for vessel noise directivity. Method name: Simplistic modelling of the vessels acoustic footprint in the shallow marine area, Keywords: Underwater noise, Shipping, Modelling