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“Sound is life in the ocean, if we pollute this channel of communication, we are condemning the ocean to irreversible change.” – Michel André

From above the surface, the ocean can seem like a relatively quiet place. Beneath it, however, is an acoustic world filled with whale songs, dolphin clicks, fish calls, snapping shrimp, waves, storms, shifting ice, and countless other sounds.

For many marine animals, sound is not simply background noise. It is information.

Sound travels efficiently through water, making it particularly useful in environments where visibility may be limited. Marine animals use acoustic information to communicate, locate food, navigate, detect predators, find mates, maintain social relationships, and understand the environment around them (National Oceanic and Atmospheric Administration [NOAA], 2024).

Cetaceans may be the most familiar example, but they are far from the only animals living in this acoustic world. Fish and many marine invertebrates also detect and respond to sound or vibration, making the marine soundscape relevant across a much broader portion of the ecosystem (Solé et al., 2023).

Humans have increasingly become part of that soundscape.

Commercial shipping, recreational vessels, military sonar, seismic exploration, dredging, pile driving, offshore construction, and other activities introduce sound into marine environments (NOAA, 2024; Solé et al., 2023). Some sources produce relatively continuous noise, while others generate short, powerful acoustic impulses.

Their effects are equally varied.

That distinction is important because ocean noise is not a single type of pollution producing a single biological response. Whether a sound affects an animal (and how) depends on factors including its frequency, intensity, duration, repetition, distance from the source, the surrounding environment, and the hearing abilities and behavioral context of the animal exposed (NOAA, 2026).

Understanding ocean noise therefore requires more nuance than simply asking whether the ocean is becoming louder.

A Changing Ocean Soundscape

Natural sound has always been part of marine ecosystems. Waves, storms, earthquakes, ice, and marine organisms themselves all contribute to the underwater soundscape. Human activity, however, has added an increasingly prominent layer of sound through commercial shipping, recreational vessels, seismic exploration, drilling, construction, and military sonar (International Whaling Commission [IWC], 2018; National Oceanic and Atmospheric Administration [NOAA], 2024).

These sources do not all affect the marine environment in the same way. The IWC (2018) distinguishes between chronic noise, such as the relatively persistent sound associated with shipping and industrial activity, and acute noise, which may be shorter in duration and higher in intensity, such as some seismic surveys and military sonar. Both forms have the potential to affect cetacean behavior and physiology. The IWC has also recognized evidence that chronic anthropogenic noise is altering acoustic environments in many regions and that compromised acoustic habitat may adversely affect some cetacean populations.

Commercial shipping is particularly important because vessels can contribute persistent, low-frequency sound across heavily traveled marine environments. For baleen whales, vessel noise can be especially relevant because many species produce relatively low-frequency sounds. These frequencies can overlap with sounds generated by vessels and other human activities, potentially interfering with biologically important acoustic signals (NOAA, 2025).

Other sources create very different acoustic conditions. Seismic surveys use powerful acoustic sources to obtain information about geological structures beneath the seafloor. Pile driving associated with marine construction generates repeated impulsive sound, while sonar systems intentionally transmit acoustic energy through the water. Recreational and commercial vessels can also alter local soundscapes, particularly in coastal habitats where marine animals and human activities frequently overlap (IWC, 2018; NOAA, 2024).

Lumping all of these sources together as simply “noise” can hide an important point: frequency, intensity, duration, repetition, and context all influence biological effects.

When Noise Masks the Message

One of the most important consequences of anthropogenic noise is acoustic masking.

Imagine trying to have a conversation while increasingly loud machinery operates beside you. The other person has not stopped speaking, and your hearing may be perfectly intact, but their voice becomes increasingly difficult to distinguish from the surrounding sound.

A similar problem can occur underwater.

Masking occurs when other sounds interfere with an animal’s ability to detect or distinguish biologically important acoustic information. For cetaceans, this is particularly significant because sound plays a fundamental role in communication, navigation, foraging, and reproduction (IWC, 2018). NOAA similarly notes that increased ocean noise can reduce animals’ ability to communicate with mates, offspring, social-group members, or feeding partners and can interfere with environmental cues used to find food, avoid predators, navigate, and locate suitable habitat (NOAA, 2024).

For cetaceans, these effects can interfere with sensory systems central to their lives. Baleen whales rely heavily on acoustic communication, while toothed whales (including dolphins, porpoises, sperm whales, and orcas) produce sophisticated social signals and use echolocation. The biological relevance of a particular source of noise depends partly on whether its acoustic characteristics overlap with what an animal can hear and the signals it needs to detect (NOAA, 2025).

Animals are not necessarily passive when their acoustic environment changes. They may alter vocal behavior, change direction, interrupt an activity, or move away from a sound source. Those responses can sometimes reduce immediate exposure, but the ability to respond does not necessarily mean the exposure is biologically insignificant. Repeated displacement, interruption of feeding, or changes in communication may carry costs of their own.

This is one reason the IWC has emphasized the need to understand noise effects not only at the level of individual animals, but also at the population level, including both acute and chronic effects (IWC, 2018).

From Behavioral Change to Physical Injury

The potential effects of underwater noise exist along a spectrum.

At some exposure levels, researchers may observe little or no measurable response. Under other conditions, animals may alter their vocalizations, feeding behavior, movement, or habitat use. Depending on the characteristics and intensity of exposure, anthropogenic sound can also produce physiological stress responses and temporary or permanent hearing loss. NOAA identifies potential effects ranging from disruption of feeding, breeding, nursing, and communication to displacement, stress responses, and auditory injury (NOAA, 2026).

The IWC (2018) similarly recognizes that exposure to certain anthropogenic underwater sounds can produce both behavioral and physiological consequences for cetaceans. Importantly, however, these effects depend on the nature of the sound and the circumstances of exposure. Not every sound source, species, or exposure scenario carries the same level of risk.

Military sonar represents one of the more serious and extensively investigated examples. Mass-stranding events involving beaked whales have repeatedly been associated with naval exercises using mid-frequency active sonar. Scientific investigations have documented pathological findings consistent with decompression sickness in some stranded animals and suggest that behavioral responses to sonar may contribute to altered diving behavior and subsequent physiological effects (Bernaldo de Quirós et al., 2019).

More recent research has continued to strengthen the association. Simonis et al. (2020), for example, examined beaked whale strandings in the Mariana Archipelago and found that half of eight documented stranding events between 2006 and 2019 occurred during or within six days of naval activity. The authors concluded that strandings of individual beaked whales can be associated with anti-submarine warfare activity and emphasized the importance of continued acoustic and visual monitoring.

This is a stronger foundation than the 2001 Washington Post article from my original piece. The historical reporting was useful in bringing attention to the issue, but subsequent peer-reviewed research allows the relationship between sonar and cetacean strandings to be discussed with greater scientific precision.

The scientifically useful question is therefore not simply whether human-generated sound can harm marine animals. It is which sounds present meaningful risks, to which animals, under which circumstances?

That nuance does not minimize the conservation problem. It helps identify where risk is greatest and where mitigation may make the greatest difference.

It Isn’t Just About Whales

Cetaceans often dominate conversations about ocean noise, and understandably so. Their sophisticated use of sound makes the connection particularly intuitive.

But the acoustic environment belongs to an entire ecosystem.

Fish use sound and other acoustic information for important biological functions, including communication, orientation, predator and prey detection, reproduction, and habitat selection. Responses to anthropogenic sound vary substantially among species and exposure conditions, reinforcing the importance of avoiding broad assumptions about how “fish” as a whole respond to noise.

Marine invertebrates broaden the picture even further.

Although they do not necessarily perceive sound in the same way vertebrates do, many marine invertebrates possess sensory structures capable of detecting acoustic particle motion and vibration. Research has documented responses to anthropogenic noise across numerous invertebrate taxa, with reported effects ranging from behavioral and physiological changes to physical effects under particular exposure conditions (Solé et al., 2023).

At the same time, the evidence base remains uneven. Solé et al. (2023) identified substantial gaps in our understanding of sound detection across invertebrate species and emphasized the need for better acoustic measurements, longer-term experiments, studies of cumulative exposure, and research across a wider range of taxa.

That uncertainty is important.

It does not mean noise is harmless to invertebrates. It means there is still much we do not know about how a major portion of marine biodiversity experiences a changing acoustic environment.

And that broader perspective changes the question.

Rather than asking only what does noise do to whales, we can begin asking how does changing the acoustic environment affect marine ecosystems?

The Challenge of Cumulative Noise

Marine animals rarely experience environmental pressures one at a time.

A whale navigating vessel traffic may simultaneously encounter changing prey availability, warming waters, chemical contaminants, fishing activity, and habitat shifts. An animal living near a developed coastline may experience vessel traffic, construction, habitat alteration, and changing environmental conditions.

This makes cumulative effects particularly difficult to understand.

A behavioral response that appears relatively minor during a single exposure may have different consequences when disturbances occur repeatedly. Leaving a feeding area once, for example, is not necessarily equivalent to repeatedly losing access to productive habitat. Similarly, a temporary interruption of communication differs from persistent masking within an important feeding, breeding, or social environment.

The IWC recognized this issue in its 2018 work on anthropogenic underwater noise, calling for greater understanding of both acute and chronic effects, consequences at the individual and population levels, the effectiveness of noise-reduction measures, and even potential indirect effects on cetaceans through changes to their prey (IWC, 2018).

That work has continued rather than ending with the 2018 report. Anthropogenic underwater noise remains a priority for the IWC Conservation Committee, and its Scientific Committee continues to investigate effects on cetaceans and approaches for reducing exposure (IWC, 2026).

This broader perspective shifts the focus from individual noisy events toward understanding the acoustic habitat itself and what happens when that habitat is repeatedly altered (NOAA, 2016).

Can We Make the Ocean Quieter?

Unlike many other forms of marine pollution, underwater noise has an unusual characteristic: once the source stops producing sound, the noise itself does not remain behind like plastic debris, oil, or a persistent chemical contaminant.

That creates opportunities for mitigation.

For commercial shipping, potential approaches include quieter vessel design, machinery maintenance, propeller improvements, operational changes, and speed management. In some circumstances, routing vessels away from sensitive habitat or adjusting the timing of particularly noisy activities may also reduce exposure.

International efforts increasingly recognize these possibilities. In 2023, the IMO approved revised guidelines for reducing underwater radiated noise from commercial shipping. The guidelines address vessel design, construction, operation, and maintenance and encourage the development of underwater-radiated-noise management plans (IMO, 2023). The revised guidelines took effect on October 1, 2023.

Technology also allows scientists to listen to the ocean in increasingly sophisticated ways.

Passive acoustic monitoring uses underwater recording equipment to detect animals, characterize soundscapes, and examine patterns in both biological and anthropogenic sound. NOAA uses passive acoustic monitoring and autonomous technologies to investigate ocean noise and its relationship with marine animal behavior and habitat (NOAA, 2026).

There is unlikely to be a single solution to ocean noise. A busy shipping corridor, offshore construction site, naval training area, and recreational boating region present different acoustic conditions and different management challenges.

Effective mitigation therefore depends on understanding which sources matter, which animals are exposed, what they are doing when exposure occurs, and which interventions can meaningfully reduce risk.

Listening Differently

When I first wrote about ocean noise in 2024, I approached it primarily as a conservation threat.

I still see that threat.

But I also see a more complicated and, in many ways, more interesting scientific story.

The evidence does not tell us that every human-generated sound produces the same response, that every species is equally vulnerable, or that every observed behavioral change will eventually become a population-level consequence. At the same time, international scientific and conservation bodies continue to recognize anthropogenic underwater noise as an important concern for cetaceans, and significant questions remain about chronic exposure, cumulative effects, population-level consequences, and the effectiveness of different mitigation strategies (IWC, 2018, 2026).

Recognizing those uncertainties does not weaken the case for taking ocean noise seriously.

Good conservation does not require overstating what science can tell us.

What the evidence does show is that sound is a meaningful component of marine habitat. Cetaceans fundamentally depend on sound, while many other marine animals also use acoustic information to communicate, navigate, locate food, avoid predators, and interpret their surroundings. Human-generated sound can interfere with those processes and, depending on the source and exposure, contribute to behavioral disruption, stress, displacement, hearing loss, and other physiological effects (IWC, 2018; NOAA, 2024, 2026).

Ocean noise is therefore about more than whether humans are making the sea “too loud.”

It is about how our activities are changing an environmental resource that countless other species evolved to depend upon.

And that may be the most important reason for us to listen more carefully.

References

Bernaldo de Quirós, Y., Fernandez, A., Baird, R. W., Brownell, R. L., Aguilar de Soto, N., Allen, D., Arbelo, M., Arregui, M., Costidis, A., Fahlman, A., Frantzis, A., Gulland, F. M. D., Iñíguez, M., Johnson, M., Komnenou, A., Koopman, H., Pabst, D. A., Roe, W. D., Sierra, E., … Schorr, G. (2019). Advances in research on the impacts of anti-submarine sonar on beaked whales. Proceedings of the Royal Society B: Biological Sciences, 286(1895), 20182533. https://doi.org/10.1098/rspb.2018.2533

‌International Maritime Organization. (2023). Revised guidelines for the reduction of underwater radiated noise from shipping to address adverse impacts on marine life (MEPC.1/Circ.906). https://wwwcdn.imo.org/localresources/en/Documents/MEPC.1-Circ.906%20-%20Revised%20Guidelines%20For%20The%20Reduction%20Of%20Underwater%20Radiated%20NoiseFrom%20Shipping%20To%20Address…%20%28Secretariat%29.pdf

International Whaling Commission. (2018). Contribution from the Secretariat of the International Whaling Commission to Part 1 of the report of the United Nations Secretary-General on Oceans and the Law of the Sea: Anthropogenic underwater noise. https://iwc.int/public/documents/FVRfm/anthropogenic_noise_UNGA_submission_FINAL.pdf

International Whaling Commission. (2026). Anthropogenic sound. https://iwc.int/management-and-conservation/environment/anthropogenic-sound‌

National Oceanic and Atmospheric Administration. (2016). Ocean noise strategy roadmap. https://oceannoise.noaa.gov/sites/default/files/2021-02/ONS_Roadmap_Final_Complete.pdf

National Oceanic and Atmospheric Administration. (2024). What is ocean noise? National Ocean Service. https://oceanservice.noaa.gov/facts/ocean-noise.html

National Oceanic and Atmospheric Administration. (2025). Marine mammal acoustics. NOAA Fisheries. https://www.fisheries.noaa.gov/new-england-mid-atlantic/science-data/marine-mammal-acoustics

National Oceanic and Atmospheric Administration. (2026). Ocean noise. NOAA Fisheries. https://www.fisheries.noaa.gov/national/science-data/ocean-noise

Simonis, A. E., Brownell, R. L., Jr., Thayre, B. J., Trickey, J. S., Oleson, E. M., Huntington, R., & Baumann-Pickering, S. (2020). Co-occurrence of beaked whale strandings and naval sonar in the Mariana Islands, Western Pacific. Proceedings of the Royal Society B: Biological Sciences, 287(1921), 20200070. https://doi.org/10.1098/rspb.2020.0070  

Solé, M., Kaifu, K., Mooney, T. A., Nedelec, S. L., Olivier, F., Radford, A. N., Vazzana, M., Wale, M. A., Semmens, J. M., Simpson, S. D., Buscaino, G., Hawkins, A., Aguilar de Soto, N., Akamatsu, T., Chauvaud, L., Day, R. D., Fitzgibbon, Q., McCauley, R. D., & André, M. (2023). Marine invertebrates and noise. Frontiers in Marine Science, 10, 1129057. https://doi.org/10.3389/fmars.2023.1129057