The impact of underwater noise pollution on marine life
- Editorial Team SDG14
- 11 minutes ago
- 5 min read
Published on 12 August 2026 at 05:10 GMT
By Editorial Team SDG14
For animals that live below the surface, the ocean is an acoustic world. Light fades quickly in water, while sound can travel over long distances. Whales, dolphins and many fish use it to locate food and predators, maintain contact, find mates, select habitat and orient themselves. The expansion of commercial shipping, offshore construction, naval activity and seismic exploration is adding both a persistent background rumble and powerful pulses to that sensory environment.
Underwater noise pollution differs from contaminants that remain after release: when a source stops, its sound stops too. Its effects, however, depend on frequency, intensity, duration, repetition, local conditions and the species exposed. A brief, high-level pulse can create an immediate risk close to its source, while chronic sound can narrow the distance across which an animal detects biologically important signals. This loss of usable acoustic space is known as masking.
A crowded spectrum
Commercial vessels create machinery vibration and propeller noise, particularly when pressure changes around fast-moving blades produce collapsing bubbles through cavitation. Because merchant traffic is widespread and recurrent, commercial shipping noise forms a near-continuous component of many ports, straits and shipping lanes. Its low-frequency energy overlaps with the calls of baleen whales and with sounds used by some fish.
Offshore construction has a different profile. Impact pile driving for wind turbines, bridges and other structures produces repeated impulsive sound, while dredging and support vessels add more continuous noise. Seismic surveys use arrays of compressed-air sources to send powerful pulses through the water and seabed, commonly at intervals over extensive survey lines. Naval activity can include active sonar, explosions and vessel noise. Sonar is deliberately designed to propagate sound and can overlap with the hearing of toothed whales, including deep-diving beaked whales.
What animals lose when sound masks sound
The National Oceanic and Atmospheric Administration reports that whales rely on sound for communication, navigation, feeding and predator avoidance. Increased background noise can obscure calls and other cues, reducing what the agency describes as listening or communication space. NOAA also reports that baleen whales may alter migration in response to seismic or industrial sound, while deep-diving toothed whales may change diving and feeding behaviour around active sonar.
Dolphins and other toothed whales use high-frequency clicks for echolocation and calls for social contact. Responses vary with context, previous exposure and behaviour at the time. Documented effects across marine animals include disturbance, displacement, stress and temporary or permanent hearing damage. Repeated disturbance can also impose costs when animals abandon feeding opportunities or spend more energy moving away.
Fish are not silent passengers in this soundscape. Many species detect pressure, particle motion or both, and use acoustic cues in spawning, territorial behaviour, predator avoidance and settlement into suitable habitat. Impulsive sound can cause injury at sufficiently high exposures, while lower levels can mask communication or change movement and feeding. The diversity of fish hearing systems makes broad predictions difficult, and evidence for one species or sound source does not automatically transfer to another.
A major scientific synthesis published in Science in 2021 concluded that human-generated sound affects marine animals from invertebrates to whales through changes in behaviour, physiology and, under some exposure conditions, survival. The authors also emphasised that soundscapes are shaped by natural and biological sound, and that habitat degradation can remove biological sounds at the same time as human noise is added. The problem is therefore not only louder machinery, but an altered acoustic habitat.
Turning down ships
The International Maritime Organization adopted revised guidelines on underwater radiated noise from commercial shipping in 2023. They describe a management process based on establishing a baseline, setting a target, selecting technical and operational measures, and monitoring results. The circular invites member states and maritime stakeholders to apply the guidance, rather than establishing a universal binding noise limit.
For new vessels, the options include designing hulls and propellers to reduce cavitation, isolating machinery vibration and modelling acoustic performance before construction. Existing ships can be assessed for propeller damage, fouling and machinery condition. Propeller polishing, hull cleaning and maintenance may reduce both noise and fuel use where poor condition is increasing resistance or cavitation.
Operational changes can include reducing speed or avoiding operating conditions that generate excessive cavitation. The IMO cautions that outcomes depend on a vessel's design and operating profile, and that safety, energy efficiency and other objectives interact. Routing and speed management around sensitive habitats can reduce exposure in a particular place or season, but may shift traffic or extend journey time. Monitoring can establish whether a measure reduces received sound where animals are present, rather than only changing a vessel's nominal settings.
Managing pulses from industry and defence
For pile driving, practical controls include quieter installation methods where engineering conditions permit, sound barriers such as bubble curtains, and sequencing work to limit exposure. Bubble curtains release compressed air around a pile to impede transmission, but performance varies with current, water depth, seabed and system design. Seasonal or spatial planning can separate the loudest activity from migration, spawning, feeding or calving periods.
The Convention on Migratory Species guidelines call for underwater noise to be considered early in environmental impact assessment. Their approach covers alternatives, baseline information, cumulative effects, modelling, monitoring and mitigation. For seismic surveys and other intense sources, measures used by regulators can include a gradual start, exclusion zones, trained visual observers, passive acoustic monitoring and shutdown or power reduction when protected animals approach. These controls reduce particular exposure risks but do not eliminate sound across the wider survey area, and detection becomes harder in poor weather, darkness or for animals spending long periods underwater.
Comparable planning tools are available for naval exercises, including choice of location and timing, acoustic modelling, lookouts and passive monitoring, and procedures to reduce or stop transmission when animals enter defined zones. Operational security and training requirements can limit public detail, making transparent assessment and cumulative monitoring relevant to understanding exposure alongside shipping, construction and exploration.
From individual projects to an acoustic habitat
One implementation challenge is cumulative noise. A construction permit, shipping route, seismic survey and naval exercise may each be assessed separately even when their sounds overlap in the same habitat. Hydrophone networks, ship-source measurements and animal-distribution data can support quieter routing, project scheduling and verification. Common measurement standards also make it easier to compare vessels and track whether retrofits work.
Measures differ in cost and maturity. Maintenance and avoiding cavitation can offer operational benefits, while major propeller retrofits, alternative foundations or redesigned survey technology require capital, engineering and sometimes longer planning. Because the IMO guidance is voluntary, its uptake can differ among jurisdictions and operators, particularly where there are no targets, disclosure rules or monitoring programmes.
The issue connects directly with SDG 14 (life below water) because acoustic conditions form part of marine habitat quality. The available controls range from source reduction and quieter design to time-area planning and real-time shutdowns. Their results depend on matching the measure to the sound source, species and location, then measuring the outcome. Without monitoring, it may be unclear whether quieter specifications have reduced exposure in the habitat concerned.
Further information:
• International Maritime Organization, Revised guidelines for the reduction of underwater radiated noise from shipping, supports the account of shipping-noise impacts, voluntary guidance and ship design, maintenance, operational and monitoring measures
• NOAA Fisheries, A whale’s world of sound, supports the explanation of masking, whale behaviour and mitigation through shutdowns and time-area controls
• Convention on Migratory Species, CMS Family Guidelines on Environmental Impact Assessments for Marine Noise-generating Activities, supports early assessment, alternatives, cumulative-impact analysis, monitoring and source-specific mitigation
• Duarte and others, The soundscape of the Anthropocene ocean, Science, supports the synthesis of effects across marine taxa and the framing of soundscape degradation
