The underwater soundscape in the port of Gothenburg and estimations of the underwater radiated noise from ships

The past decade underwater noise has gained increased attention due to its potential negative impact on the marine environment. In Swedish waters there have only been a few studies of the underwater soundscape in harbour environments. This study aims to increase the knowledge in this field, first by investigating the soundscape in a specific area, and second by developing a framework for automatic acquisition of underwater radiated noise (URN) from ships from opportunistic measurement data. For the first step, three positions with different acoustic environments, in and around the port of Gothenburg were chosen. The port includes an important habitat for many fish species, as one of the largest rivers of Sweden has its outflow in the area. The area is also exposed to intense ship traffic and other port activities. Influencing factors on the measured sound pressure level (SPL) were the number of ship passages and their distance from each position. Natural sound events and other identified anthropogenic noise sources had minor impact on the SPL. The acoustic environmental parameters, such as bottom type and topography, as well as the sound speed profiles are well-known to effect the measured SPL, however, these were outside the scope of this study. For the second step, a method using data on ship movements from AIS and measured SPL data was developed. The results showed that the method works well to estimate the URN from ship for certain frequencies. More validation is needed to verify the method for the full bandwidth of typical ship URN.