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Underwater Noise Thematic Assessment

Executive summary

Anthropogenic noise in the OSPAR Maritime Area can be continuous (mainly from shipping) or impulsive (e.g. from seismic surveys, explosions and pile driving). Noise can interfere with the hearing or physiology of marine animals or cause behavioural disturbance or injury. Shipping noise and impulsive noise are particularly intense in the Greater North Sea. Measures to mitigate impulsive noise have had some impact, but international guidelines on reducing continuous noise appear to have had little effect to date. OSPAR has committed to producing a regional action plan of measures to reduce noise, and to improving the monitoring of noise levels.

More detailed information on the assessments of pressure and state relating to anthropogenic noise can be found in the OSPAR Common and Candidate Indicators here ; more information (including further references) on activities contributing to anthropogenic noise can be found in the series of feeder reports here .

Q1. Identify the problems? Are they the same in all OSPAR regions?

Noise can affect marine animals by interfering with their ability to communicate, navigate, find food, or detect threats; by provoking fleeing or distraction; or by causing injury or death. As yet there is no agreed definition of good environmental status for underwater noise, but OSPAR has committed to reducing noise pollution in the OSPAR Maritime Area.

The dominant source of continuous underwater noise is shipping; other sources include recreational boating, fishing, aggregates extraction, oil and gas activities, and offshore wind turbines. As yet, only the Greater North Sea is covered by an OSPAR assessment for continuous noise. In large areas of the Southern North Sea, and along major shipping routes, the noise exceeds natural sound in the low frequency bands by over 20 dB for over 50% of the time.

Impulsive noise is produced by seismic air gun surveys, pile driving for offshore wind turbines and other construction, explosions, military activities, and some acoustic deterrent devices. Reported impulsive noise increased from 2015 to 2019, with most activity in the OSPAR Maritime Area occurring in the Greater North Sea. Since data are unavailable for some Contracting Parties and sound sources, the data underestimates this activity. The risk of disturbance to harbour porpoise from reported impulsive noise decreased from 2015 to 2017, then increased to 2019.

For both impulsive and continuous noise, it is not yet possible to establish any definitive long-term trends in noise levels, including since the Quality Status Report 2010 (QSR 2010).

Activity type of Pulse Block Days reported for 2015. Available at: ODIMS

Activity type of Pulse Block Days reported for 2018. Available at: ODIMS

Activity type of Pulse Block Days reported for 2016. Available at: ODIMS

Activity type of Pulse Block Days reported for 2019. Available at: ODIMS

Activity type of Pulse Block Days reported for 2017. Available at: ODIMS

Activity type of Pulse Block Days reported for 2015-2019

Q2. What has been done?

For both types of noise OSPAR has developed a monitoring programme and has contributed to the development and maturing of assessment methodologies. The programme for impulsive noise has been operational since 2016, and is in line with the guidance from the European Union (EU) Technical Group on Underwater Noise (TG Noise). The monitoring of continuous noise has been taken forward through the JOMOPANS and JONAS projects, although it is still under development by the Contracting Parties.

The International Maritime Organization (IMO) has produced voluntary guidelines on noise reduction, including from key sources such as propellers or machinery vibrations. It is possible to reduce noise from shipping through technical measures, such as hull and propeller design, and operational measures such as spatial restrictions or reducing shipping speeds.

For percussive pile driving, technical measures to mitigate adverse effects include the use of bubble curtains, isolation casings and hydro sound dampers. These measures are very effective in reducing levels of impulsive noise from pile driving in the OSPAR Maritime Area. Alternative, quieter, installation methods such as suction buckets and drilling can also be used in some areas. Bubble curtains could be used to abate noise from the detonation of unexploded ordnance (UXO), although this is unlikely to be practical in most situations.

Pile driving operation with bubble curtain. © Trianel/Lang

Pile driving operation with bubble curtain. © Trianel/Lang

For geophysical surveying, noise from seismic surveys can be reduced to a small extent by changes in the design and configuration of airgun arrays. To achieve significant reductions, alternative technologies are needed; marine vibrator technologies are under development.

Operational measures can also be taken to reduce the risk of adverse effects, including injury, of impulsive noise on sensitive species, such as use of acoustic deterrent devices, choice of less critical times or areas for activity (e.g. avoiding feeding areas, reproductive sites or migration routes), and use of marine mammal observers or acoustic monitoring to detect animals in the vicinity of operations.

National standards for noise management have been put in place by several OSPAR Contracting Parties.

Q3. Did it work?

To date, it is thought that the 2014 IMO voluntary guidelines have not yet had an effect on overall shipping noise, and IMO has adopted the initiative of Canada, USA and Australia to review and update these guidelines. The review should be finished by 2023.

The OSPAR Common Indicator on the Risk of Impact from Impulsive Noise has reported some reduction in noise exposure for harbour porpoise as a result of measures taken to reduce noise from piling activity. Further abatement measures in future would improve upon this risk reduction.

Through its indicator assessments, OSPAR has contributed to the awareness of underwater noise pollution among various groups, such as policy makers, scientists, industry, non-governmental organisations, and the general public.

Q4. How does this field affect the overall quality status?

At the time of writing, there are not yet agreed threshold values for underwater noise, but OSPAR nevertheless considers that noise should be reduced to levels that do not adversely affect the marine environment. However, work is ongoing to develop such threshold values within OSPAR, HELCOM and the EU.

Q5. What do we do next?

The North-East Atlantic Environmental Strategy 2030 (NEAES 2030) commits OSPAR to producing a regional action plan, by 2025, of measures to reduce noise pollution and to implementing, by 2022, a monitoring programme for continuous sound in the OSPAR Maritime Area, taking account of developments in the EU. The action plan will bring together the best from the Contracting Party scientific and policy communities and will:

  • develop and manage a programme of prioritised actions on reducing pressure from underwater noise, to be implemented from 2025 (or earlier where possible);
  • be supported by:
    • monitoring and assessment programmes for all OSPAR regions;
    • assessments of the latest evidence on harm;
    • risk assessments for additional species and habitats beyond harbour porpoise;
    • models and analysis to identify and develop Best Available Techniques (BAT) and Best Environmental Practice (BEP) for measures to achieve agreed threshold values and targets.

It will:

  • include all significant sources of both impulsive and continuous underwater noise;
  • add value to other regional and global measures and processes, for example by developing local and regional-scale measures in accordance with IMO guidance and standards;
  • support the delivery of other operational objectives in the NEAES 2030, in particular objectives to enable the recovery of marine species and habitats and to increase resilience;
  • give priority to measures to enable the recovery of OSPAR-listed threatened and / or declining species and habitats.

Priority areas include:

  • engaging with IMO on the review of guidelines for noise reduction from shipping, and identifying and implementing ways to improve the uptake of this guidance by shipping using the OSPAR Maritime Area;
  • assessing national standards in OSPAR Contracting Parties for the reduction of impulsive noise from piling, and promoting the implementation of BAT and BEP;
  • assessing and promoting the implementation of BAT and BEP in reducing other sources of impulsive noise, including from seismic surveys and the removal of UXO;
  • identifying and implementing options for reducing adverse impacts of underwater noise on marine protected areas (MPAs), in particular those important for species known to be particularly sensitive to underwater noise;
  • further improving the extent and quality of reporting to the OSPAR Impulsive Noise Register, and of the validation of models used to assess continuous noise.

Underwater Noise Assessments


Lead authors: Terence Ilott, Niels Kinneging, Alexander Liebschner and Nathan Merchant

Supporting authors: Bee Berx, Adrian Judd

Supported by: Intersessional Correspondence Group on Underwater Noise, Intersessional Correspondence Group on the delivery for the Quality Status Report, Intersessional Correspondence Group on Economic the Social Analysis, Climate Change Expert Group and the OSPAR Secretariat


OSPAR, 2023. Underwater Noise Thematic Assessment. In: OSPAR, 2023: Quality Status Report 2023. OSPAR Commission, London. Available at:

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