Ocean noise and our path to quiet seas

Underwater noise pollution has drastically increased over the last few decades. Commercial shipping alone has led to a 128-fold increase in sound intensity since the mid-twentieth century. This is largely due to the expansion of marine commercial routes, oil and gas exploration, and offshore construction.

Sources of ocean sound

To understand the impact of underwater noise, it helps to know where it comes from. Ocean sounds fall into three broad categories:

• Geophony: Natural sounds like wind, rain, and seismic activity

• Biophony: Sounds made by marine life, such as whale songs, fish grunts, and the clicks of invertebrates

• Anthropophony: Sounds introduced by human activities, ranging from continuous noises like shipping and drilling to pulsed sounds from pile driving, seismic surveys, and explosions.

While natural and biological sounds have been around for millions of years, human-generated noise has rapidly increased to levels now proven harmful to individuals and entire ecosystems.

How noise affects marine life

Sound travels incredibly efficiently through water, often over long distances. This, combined with constant human marine activities, poses problems for marine life. Underwater noise can disrupt entire marine ecosystems by interfering with how animals communicate, navigate, find food, and perform other vital life functions. Constant exposure to high noise levels can lead to stress, behavioural changes, hearing loss, and even physical harm to marine mammals, fish, and invertebrates, with potential long-term impacts on their populations.

The silent revolution: Regulating underwater noise

Fortunately, the issue of underwater noise has gained significant attention from governments, regulators, industry, and scientists. As awareness of its impact on biodiversity and marine environments has grown, so has the drive to develop regulations and technologies to assess, monitor, and reduce underwater noise. These efforts are crucial for protecting marine habitats and ensuring the sustainability of our ocean resources.

Underwater noise is now internationally recognised as a pollutant, leading to new legal frameworks aimed at reducing its impact. For example, in Europe, the Marine Strategy Framework Directive addresses anthropogenic noise in the marine environment, while in the United States, legislation like the Marine Mammal Protection Act and the Endangered Species Act help regulate human activities affecting aquatic animals.

Under this evolving regulatory landscape, projects are increasingly required to demonstrate minimal environmental impact. Stricter limits on permissible noise levels mean that access to professional services for predicting, monitoring, and mitigating underwater noise is becoming essential.

Understanding underwater acoustic services

For organisations operating in marine environments, understanding how sound behaves underwater is no longer optional, it’s central to responsible planning and compliance. Whether you're managing vessel traffic, conducting seismic surveys, or planning offshore construction, underwater noise can have significant implications for both biodiversity and project viability.

Here are three key areas to consider when evaluating underwater acoustic services:

• Sound source characterisation: Every marine activity generates sound, but not all sounds are equal. To assess potential impacts, it is essential to understand the source level, which is essentially how loud a sound is at its origin. This can be estimated through direct measurement techniques like sound source verification (SSV), which involves capturing sound at various distances and working backwards, or through modelling based on known characteristics of specific sources (e.g. vessels, pile drivers, seismic arrays). SSV is often preferred because it reflects real-world conditions and provides more reliable data.

• Sound field mapping: Once the source is understood, the next step is predicting how sound travels through the marine environment. This is influenced by factors like water depth, seabed composition, and temperature. Advanced propagation models can simulate sound spread in three dimensions, helping you visualise where noise will travel and how intense it will be. These maps are vital for identifying areas of concern, planning mitigation strategies, and communicating potential impacts to regulators and stakeholders.

• Noise impact assessment: Regulators increasingly require evidence that marine operations won’t harm sensitive species. This involves comparing predicted sound levels to biological thresholds or levels at which animals may experience behavioural changes, hearing loss, or other effects. By identifying zones where these thresholds are exceeded, you can plan mitigation measures such as exclusion zones or real-time monitoring. Looking ahead, assessments are evolving to consider population-level effects, especially for species that rely heavily on sound for survival.

Tools for a complex challenge

Effectively managing underwater noise begins with understanding how sound behaves in different marine environments. At Fugro, we’ve created internal software to support our clients and our own operations by modelling the acoustic footprint of offshore activities and assessing their potential impact on marine life. This includes estimating the sound power of various sources, predicting how sound diminishes over distance, and identifying mitigation zones, areas where marine animals may be exposed to behavioural disturbances, temporary hearing shifts, or more serious outcomes such as hearing damage.

The software incorporates source models for common marine activities like seismic surveys, impact pile driving, unexploded ordnance (UXO) clearance, and vessel traffic. It also uses advanced propagation models to simulate sound travel with high accuracy. Future developments will expand its capabilities to include assessments of population-level effects, an increasingly important consideration in environmental impact evaluations.

Quieter seas are possible

The ability to predict and assess underwater noise is no longer good to have, it’s become a fundamental part of responsible marine operations. As regulatory expectations evolve and awareness of acoustic impacts grows, companies have an opportunity to lead by example. By understanding and managing the acoustic footprint of their activities, organisations can not only streamline permitting processes but also contribute meaningfully to the protection of marine ecosystems.

The path to quieter seas is achievable, but it requires collaboration, transparency, and informed decision-making. With the right tools and expertise, we can help ensure that marine development and environmental stewardship go hand in hand.