Background The Baltic Sea is one of the world’s largest semi-enclosed bodies of brackish water. The special geographical, oceanographic and climatological characteristics of the Baltic ecosystem make it highly susceptible to the environmental impacts of human activities at sea and in its catchment area. As a result of this status, the International Maritime Organization (IMO) has designated the Baltic Sea as one of 12 ’Particularly Sensitive Sea Areas’ (PSSAs) in the world. During the past few decades, the level of human-introduced underwater noise has increased in the marine environment. Major sound sources are shipping, seismic surveys for oil and gas exploration, offshore construction such as marine wind farms, military and mapping sonars, offshore industrial activities such as dredging, drilling and the use of explosives, and the use of acoustic deterrent devices. In the Baltic Sea, the largest contributor to human-induced underwater noise is commercial shipping and the number of ships is set to double by 2030. The size of the ships is also expected to increase, potentially increasing the noise levels. The European wind energy sector is also experiencing a strong growth. The construction of renewable energy sources has a considerable impact on the local marine ecosystem. Objectives The overall goal of the BIAS project is to ensure that the introduction of underwater noise is at levels that do not adversely affect the marine environment of the Baltic Sea. Specific objectives of the project: To establish and implement standards and tools for the management of underwater noise in accordance with the Maritime Strategy Framework Directive (MSFD) in the marine region of the Baltic Sea. The BIAS standards and tools will be state of the art, supported by the expert community, match the needs for management of underwater noise in accordance with the MSFD, be harmonised across the Baltic Sea region, and be valuable for future activities after the end of the project; To demonstrate the national and regional advantages of a transnational approach for management of underwater noise in accordance with the MSFD. A transnational approach is a prerequisite for successful management of underwater noise; To produce soundscape maps showing the underwater noise generated by commercial vessels. These soundscape maps will serve as the initial assessment in accordance with the MSFD, as the most central input to the GIS-based planning tool that will be implemented, and as the baseline in future monitoring programmes in accordance with the MSFD; To implement a user-friendly planning tool designed for a straightforward management of human-induced underwater noise. The tool will be GIS-based and consist of the soundscape maps showing the initial assessment of underwater noise, and simplified calculations for the management of intermittent sound sources (e.g. piling and underwater explosions); To establish for recording, handling and processing data on underwater noise in accordance with the MSFD; and To establish standards for hardware specifications, handling of sensors, handling of data and a data-sharing platform. Expected results: A basis for standardised and appropriate management of underwater noise in the Baltic Sea in all EU Member States bordering the Baltic Sea; A plan for cost-efficient and regionally coordinated management of underwater noise in the Baltic Sea; GIS layers that will serve as a basis for future management decisions on human activities generating underwater noise and for future evaluation of indicators on the environmental status of the Baltic Sea; The BIAS tool to have been demonstrated to all other EU Member States bordering the Baltic Sea; Publicly available state-of-the-art, regionally adapted standards for recording, handling and processing data on underwater noise in the Baltic Sea; and A publicly available data-sharing platform containing standardised and quality assured data on Baltic underwater noise.