–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–
Of all the ways to sense objects in the ocean, sound reaches the furthest. Light seldom travels more than hundreds of meters in the ocean, but sound can travel thousands of kilometers. For example, the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) created a network of just 6 hydrophones (underwater microphones) that can detect a nuclear explosion anywhere in the global oceans (Figure 1).
Figure 1. Map of 6 underwater acoustic sensing stations of the Comprehensive Test-Ban Treaty Organization.
Reproduced with permission from Ainslie, Michael A., et al. “Ocean soundscapes and trends from 2003 to 2021: 10–100 Hz.” The Journal of the Acoustical Society of America 157.6 (2025):4358-4384, Figure 1.
Sound can travel so far that listening has long been selected for detecting threats such as submarines, but the ocean carries acoustic signals of wind, waves, rain and sea ice that are important for monitoring climate change, and the sounds of animals vocalizing underwater tell us about their distribution and about the health of marine ecosystems.
Using sound to understand changes in the ocean requires many years of data to sort out changes on daily, seasonal, and longer-term time scales. The CTBTO hydrophone array is one of few sources of such long time series of ocean sound.
Figure 2. Measured and modeled Sound Pressure Level in the 10-40 Hz band from Wake Island in the Pacific Ocean. Reproduced with permission from Robinson, Stephen, et al. “Impact of the COVID-19 pandemic on levels of deep-ocean acoustic noise.” Scientific Reports13.1 (2023): 4631, Figure 2. Creative Commons Attribution 4.0 International License
Figure 2 shows 12 years of low frequency acoustic data from the Pacific. The strongest pattern in sound level is annual variation, but you can also see a longer-term pattern of increasing variation from 2010 to 2020.
Figure 3. Expanded view of sound level data from figure 2, here from 2018-2020. Reproduced with permission from Robinson, Stephen, et al. “Impact of the COVID-19 pandemic on levels of deep-ocean acoustic noise.” Scientific Reports13.1 (2023): 4631, Figure 4. Creative Commons Attribution 4.0 International License
Analyzing data from before COVID hit in 2020, shown with blue dots in figure 3, makes it possible to estimate what sound levels were expected in 2020 based on earlier years. The data points change color from blue to red once COVID started to affect seagoing activities. You can see that many of the red dots from January to July 2020 are lower than the gray area predicted from pre-COVID data, demonstrating that the reduction in human activities during COVID reduced sound levels around Wake Island.
Excessive sound can also harm wildlife by damaging hearing and by causing stress or disturbance. Recordings from the west coast of the US have shown that increased shipping caused underwater sound energy to more than double each decade from the 1960s to the 1990s. This increase in human-generated ocean noise stimulated concerns about increasing effects of noise on marine life. In June 2025, a coalition of 37 countries declared “ocean noise is intensifying, driven by the ongoing expansion of global shipping activities and development of ocean industries” and formed a high ambition coalition for a quiet ocean (https://www.foraquietocean.org).
Figure 4. Trends in annual mean sound pressure level (SPL) from 2006-2021 at Ascension Island at 5 frequency bands: VLF=9-14 Hz; LF=14-28 Hz, MF=28-56 Hz; HF=56-112 Hz; ADEON B = 9-89 Hz. Reproduced with permission from Ainslie, Michael A., et al. “Ocean soundscapes and trends from 2003 to 2021: 10–100 Hz.” The Journal of the Acoustical Society of America 157.6 (2025):4358-4384, Figure 18.
Analysis of CTBTO data from sites around the world document changes in ocean sound after 2000. This century has not seen significant increases in sound pressure level at any of the CTBTO sites. Figure 4 shows the long term decline in sound level in 4 frequency bands from 2006-2021 at Ascension Island in the Atlantic Ocean. A close look at the acoustic record (Figure 5A) shows that airguns used to prospect for offshore oil and gas along the African and South American coasts were a primary source. Figure 5B shows that the best predictor of sound pressure level there in the MF band is the price of Brent Crude Oil. When the price of oil is low, there are fewer surveys. The major sources of sound energy varied between sites and included natural sounds of earthquakes and whales and sounds of human activities such as shipping.
Figure 5. 5A shows a waveform on the top and spectrogram (plot of frequency against time) of a series of pulses from an airgun source recorded from the CTBTO station at Ascension Island. Figure 5B shows how the sound level recorded there correlates with the price of oil. Reproduced with permission from Ainslie, Michael A., et al. “Ocean soundscapes and trends from 2003 to 2021: 10–100 Hz.” The Journal of the Acoustical Society of America 157.6 (2025):4358-4384, 5A: Figure 16; 5B Figure 20.
Access to long time series of ocean sound data is critical for understanding how changes in sound sources cause trends in ocean sound. This information is not only critical for estimating indicators of climate change and ocean health, but also for managing the effects of sound. Noise from human activities may not have been increasing ocean sound levels globally in this century, but sound produced by more localized activities and the harm it causes to wildlife needs to be measured and managed.
Over the last 50 years, the integration of global weather data with improved computer models has drastically improved our ability to forecast weather. The applications of ocean sound to measure threats, climate change and ecosystem health are so important that we need similar expansion and improvement of our global ocean sound observation networks so that we can forecast and manage these important applications.
Monterey Bay Aquarium Research Institute, Moss Landing, CA, 95039, United States
Popular version of 4aUW7 – Wind-driven movement ecology of blue whales detected by acoustic vector sensing
Presented at the 188th ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0038108
–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–
A technology that captures multiple dimensions of underwater sound is revealing how blue whales live, thereby informing whale conservation.
The most massive animal ever to evolve on Earth, the blue whale, needs a lot of food. Finding that food in a vast foraging habitat is challenging, and these giants must travel far and wide in search of it. The searching that leads them to life-sustaining nutrition can also lead them to a life-ending collision with a massive fast-moving ship. To support the recovery of this endangered species, we must understand where and how the whales live, and how human activities intersect with whale lives.
Toward better understanding and protecting blue whales in the California Current ecosystem, an interdisciplinary team of scientists is applying a technology called an acoustic vector sensor. Sitting just above the seafloor, this technology receives the powerful sounds produced by blue whales and quantifies changes in both pressure and particle motion that are caused by the sound waves. The pressure signal reveals the type of sound produced. The particle motion signal points to where the sound originated, thereby providing spatial information on the whales.
A blue whale in the California Current ecosystem. Image Credit: Goldbogen Lab of Stanford University / Duke Marine Robotics and Remote Sensing Lab; NMFS Permit 16111.
For blue whales, it is all about the thrill of the krill. Krill are small-bodied crustaceans that can form massive swarms. Blue whales only eat krill, and they locate swarms to consume krill by the millions (would that be krillions?). Krill form dense swarms in association with cold plumes of water that result from a wind-driven circulation called upwelling. Sensors riding on the backs of blue whales reveal that the whales can track cold plumes precisely and persistently when they are foraging.
The close relationships between upwelling and blue whale movements motivates the hypothesis that the whales move farther offshore when upwelling habitat expands farther offshore, as occurs during years with stronger wind-driven upwelling. We tested this hypothesis by tracking upwelling conditions and blue whale locations over a three-year period. As upwelling doubled over the study period, the percentage of blue whale calls originating from offshore habitat also nearly doubled. A shift in habitat occupancy offshore, where the shipping lanes exist, also brings higher risk of fatal collisions with ships.
However, there is good news for blue whales and other whale species in this region. Reducing ship speeds can greatly reduce the risk of ship-whale collisions. An innovative partnership, Protecting Blue Whales and Blue Skies, has been fostering voluntary speed reductions for large vessels over the last decade. This program has expanded to cover a great stretch of the California coast, and the growing participation of shipping companies is a powerful and welcome contribution to whale conservation.
Alba Solsona-Berga – asolsonaberga@ucsd.edu Scripps Institution of Oceanography University of California San Diego La Jolla, CA 92037 United States
Instagram: @sripps_mbarc
Popular version of 2pAO5 – Shaping the acoustic field in the Gulf of Mexico: marine mammals linked to topography and oceanographic features Presented at the 188th ASA Meeting Read the abstract at https://doi.org/10.1121/10.0037682
–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–
Exploring the Lives of the Ocean’s Deepest Divers After the Deepwater Horizon oil spill, restoring marine mammal populations in the Gulf of Mexico became a priority. Protecting these animals starts with understanding how they use their habitat and where they go. Sperm whales and beaked whales are some of the ocean’s most extreme divers, spending much of their lives navigating the dark depths. They rely on bursts of sound called echolocation clicks to find their prey and navigate. These clicks act like acoustic fingerprints, helping us figure out where whales go and what environments they prefer.
To track their movements, we set up 18 underwater listening stations throughout the Gulf. These instruments recorded sounds continuously for three years. By analyzing this data, we discovered patterns in where the whales appeared and how those locations were linked to oceanographic features like currents and slopes.
Video: Deploying the instruments.
Where Whales Go Different whale species tend to favor different parts of the deep Gulf. Goose-beaked whales often stay near deep eddies and steep slopes. Gervais’ beaked whales are more likely to follow surface and midwater eddies, while sperm whales mostly stick to areas where freshwater from rivers mixes with the open ocean. They tend to avoid the tropical Loop Current, a warm flow from the Caribbean into the Gulf, that seems to create conditions less favorable for these whales.
An example of how marine mammals use different parts of the Gulf of Mexico. The maps show ocean features at three depth ranges: surface (0-250 m), mid-depth (700-1250 m), and deep (1500-3000 m). Dolphins are shown in the surface plot, sperm whales in the mid-depth plot, and goose-beaked whales in the deep plot. Colors indicate water movement, with red showing strong currents and blue showing calmer areas. Circles mark recording stations, with bigger circles showing more animals detected.
Whales Shape Their Environment Whales don’t just adapt to their surroundings, they also shape them. Their powerful clicks, produced by the millions, bounce off the seafloor and underwater features, making their presence a key part of the local acoustic environment. Where whales occur, the acoustic environment changes, influenced both by their vocalizations and by the prey that may be present. Prey layers can influence how sound propagates through the water, adding complexity to the acoustic field. Detecting whales in specific areas helps us understand how the acoustic environment might vary under different conditions. Mapping where whales are present also reveals potential biological hotspots and helps us understand how sound behaves in these deep-sea habitats.
Why This Matters This research is a collaboration between scientists from the United States and Mexico, supported by NOAA’s RESTORE Science Program, the Deepwater Horizon Restoration Open Ocean Marine Mammal Trustee Implementation Group, and the Office of Naval Research Task Force Ocean. These detailed maps of whale distribution are vital for identifying critical habitats and guiding conservation strategies. They help us understand how threats like oil spills, industrial activity, and environmental changes impact whale populations, allowing us to plan effective mitigation and restoration efforts to maintain healthy ecosystems.
Brandyn Lucca – blucca@uw.edu
Bluesky: @brandynlucca.bsky.social
Instagram: @brandynmark
Applied Physics Laboratory, University of Washington, Henderson Hall (HND), 1013 NE 40th St, Seattle, Washington, 98105, United States
Joseph Warren
Instagram: @warren.bioacoustics.lab
Bluesky: @warren-lab.bsky.social
Affiliation: School of Marine and Atmospheric Sciences, Stony Brook University
Popular version of 2aAO9 – Active acoustic detection of fish and zooplankton along bathymetric features of the New York Bight
Presented at the 188th ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0037522
–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–
Imagine standing on the beach in New York City, looking beyond the harbor over the horizon where rolling waves meet an armada of ships lined up to unload their cargo. What remains hidden from view are the vast underwater plains, valleys, and canyons teeming with marine life beneath the surface. From a bird’s-eye view, this area forms the New York Bight, a stretch of ocean off the coast of New York City situated between southern New Jersey and eastern Long Island. This seascape offers prime real estate for animals ranging from copepods to whales.
Some animals often gather along the shelfbreak, where the relatively flat, shallow seafloor of the continental shelf dramatically changes to the deep sea. Others prefer life in a well-known ecological hotspot and one of the largest marine canyons in the world: the Hudson Canyon. Like many people, marine animals choose habitats based on the amenities they offer, but their preferences can evolve as they age or in response to environmental shifts. Some may leave the New York Bight entirely, while others may settle in undiscovered hotspots elsewhere. But how can scientists find these hotspots in the first place?
How do scientists “see” beneath the waves?
Researchers use a technique called “active acoustics” to get snapshots of where animals are in the water column across large areas that can complement other sampling methods like nets. With this approach, they send out short pulses of sound from a moving ship and measure the echoes that bounce back from the seafloor or are created from animals that live in the water column. The equipment scientists use to measure these echoes is similar to bottom-finders and fish-finding systems used by fishers and boaters. The results can reveal dense fish schools clustered along the steep walls of a canyon or zooplankton aggregations in the near-surface waters along the shelfbreak. These patterns help scientists better understand how seascapes shape habitat preferences among marine organisms (Figure 1).
Echograms are one way to visualize acoustic backscatter, with color scale units corresponding to the total energy in echoes measured from marine organisms. This echogram reveals how animals are distributed vertically in the water column along a ship transect that crossed the Hudson Canyon. The dark gray region corresponds to the seafloor.
To carry out this research, scientists measure echoes from animals in the water column, collect fish and zooplankton using nets and trawls, and measure how temperature and salinity (and other environmental factors like oxygen) vary in the ocean as you go down in depth. Researchers collected the data for this study during seasonal surveys aboard a research vessel that covered the waters south of Long Island, New York, out to the shelfbreak, approximately 140 miles away (Figure 2).
Acoustic surveys were conducted along seven transect lines (black lines) with biological and seawater sampling stations at each square point. The white lines represent isobaths, or lines of constant depth, at 25, 50, 100, 500, 100, and 2000 m. The orange and red stars indicate where the Hudson Shelf Valley and Hudson Canyon begin.
Location, location, location: Hotspots change with the seasons
The New York Bight regions with the most fish and zooplankton (as measured by our echosounders) change with the seasons. In winter and early spring, most organisms concentrated farther offshore, often along the canyon edges or beyond the shelfbreak. As summer arrives, these biological hotspots grow along the shelfbreak, especially in and around the canyons, and move closer to shore. By fall, acoustic measurements showed that fish and zooplankton spread more evenly across the continental shelf.
For fish living near the seafloor, a seasonal feature called the Mid-Atlantic Cold Pool plays a major role in their movements. This layer of cold water forms on and above the seafloor over part of the continental shelf each spring and slowly decreases in volume throughout the summer. When the Cold Pool forms, many near-bottom fish shift away from their spatial extent due to the fish having temperature preferences and gather in the Hudson Canyon, other shelfbreak canyons, inshore areas, and the Hudson Shelf Valley. As the Cold Pool shrinks in late summer, their distribution becomes more like the broader patterns observed for overall biological backscatter (Figure 3).
An example echogram of biological backscatter near the shelfbreak. The 9º (gray) and 10º (black) isotherms, or lines of constant temperature, approximate the lateral and vertical extent of the Mid-Atlantic Cold Pool that, in this case, nearly walled this aggregation off from the inshore waters on the continental shelf entirely.
From underwater sound to action: Guiding management decisions
The New York Bight is a dynamic and productive ecosystem that experiences significant fishing pressure, shipping activity, and offshore energy development. By combining acoustic surveys with biological net sampling and oceanographic measurements, scientists can identify areas that fish and zooplankton may prefer (or avoid) throughout the year. Surveys such as this one help guide management decisions that balance the economic and commercial health of the New York Bight.
Michael Stocker – mstocker@OCR.org
Bluesky: @ocean-noise.bsky.social
Instagram: @oceanconservationresearch
PO Box 559, Lagunitas, CA, 94938-0559, United States
Popular version of 4aAB9 – Underwater Internet of Things: Industrial boon, biological headache
Presented at the 188th ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0037992
–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–
As the technologies of commerce and industry expand out into the sea, so does the need to localize, query, and control these technologies. Due to the challenges of physically accessing underwater equipment, a digital “Underwater Internet of Things” is being developed for marine enterprises.
Due to the opacity of water to radio frequency electromagnetic energy – which we use for our above water WiFi and Blue Tooth and other communication connections, underwater communication channels predominantly use sound. This is particularly the case as distances between the communication nodes increase.
Seafloor processing equipment for oil and gas extraction equipment (Nautronix illustration)
The efficiency of sound transmission through water has not been lost on evolution; pretty much all marine and aquatic animals use sound to get around. From the simple clicks and grunts of marine invertebrates and fishes, to the complex and beautiful songs of humpback whales. In fact sound transmits so efficiently in water that some whales can project sounds over thousands of kilometers.
The ocean is alive with sound, and marine animals have evolved and adapted to utilize “acoustical niches” appropriate to their particular habitats; dolphins using high-frequency, short wavelength biosonar for near-field echolocation, large whales using low-frequency, long wavelength sounds for long distance communication and navigation. And all the critters in between – fishes, lobsters, krill, and benthic worms, all have their own habitat-adapted sound repertoires.
So herein lies the conflict with the acoustic Underwater Internet of Things (UIoT): The frequencies of the sounds being used to control and query underwater equipment overlaps the various existing bioacoustic communication channels. And while the sheer density of this technological noise threatens to obscure or “mask” important bioacoustic communication channels, the sound qualities of the common digital signals themselves threaten to turn the ocean acoustic environment into a living acoustical nightmare.
Digital communication hinges on unambiguous data states – strings of “ones and zeros” that code into data channels. Acoustically this translates into ripping streams of “noise-not noise” signals. The problem with this in the realm of bioacoustics is that these data streams sound horrible. They are also clearly associated with hearing damage in humans and other animals.
This nasty noise problem is exacerbated by the fact that the most useful transmission frequencies for commerce and industry fall in the 1kHz to 50kHz frequency range, which resides in the ‘sweet spot’ for dolphins and porpoises, and overlaps the hearing ranges of most other marine animals.
Working with the International Standards Organization (ISO) and the International Electrotechnical Commission (IEC), we are urging industry to use signals that are less damaging to marine life. This would include “transmit on query only” and synchronized, spread spectrum “frequency hopping” schemes,* and using bio-mimetic signals which would sound more like dolphins or whales and less like giant fingernails scratching across a dirty chalkboard.
* “Spread Spectrum, frequency hopping” technology was patented by 1940s-50s glamour actress Lana Turner. The premise being that the transmitter and the receiver are synchronized over a coded series of transmission channel frequencies. Transmission only occurs at a specific time over a specific frequency channel. In this way the communication channel becomes impervious to noise, so the signal level can be below the ambient noise level. A variation of this technology makes it possible to have millions of cell phones operating in the same radio frequency band without interference.
MELVILLE, N.Y., Nov. 21, 2024 – Mysterious, repeating sounds from the depths of the ocean can be terrifying to some, but in the 1980s, they presented a unique look at an underwater soundscape.
In July 1982, researchers in New Zealand recorded unidentifiable sounds as a part of an experiment to characterize the soundscape of the South Fiji Basin. The sound consisted of four short bursts resembling a quack, which inspired the name of the sound “Bio-Duck.”
Looking from the stern of the ship as it tows the long horizontal array of hydrophones. The tow cable can be seen going through the metal horn at the stern. The hydrophone array is several hundred meters behind the ship and about 200 meters deep. Credit: Ross Chapman
“The sound was so repeatable, we couldn’t believe at first that it was biological,” said researcher Ross Chapman from the University of Victoria. “But in talking to other colleagues in Australia about the data, we discovered that a similar sound was heard quite often in other regions around New Zealand and Australia.”
They came to a consensus that the sounds had to be biological.
Chapman will present his work analyzing the mystery sounds Thursday, Nov. 21, at 10:05 a.m. ET as part of the virtual 187th Meeting of the Acoustical Society of America, running Nov. 18-22, 2024.
“I became involved in the analysis of the data from the experiment in 1986,” Chapman said. “We discovered that the data contained a gold mine of new information about many kinds of sound in the ocean, including sounds from marine mammals.”
“You have to understand that this type of study of ocean noise was in its infancy in those days. As it turned out, we learned something new about sound in the ocean every day as we looked further into the data—it was really an exciting time for us,” he said.
However, the sounds have never been conclusively identified. There are theories the sounds were made by Antarctic Minke whales, since the sounds were also recorded in Antarctic waters in later years, but there was no independent evidence from visual sightings of the whales making the sounds in the New Zealand data.
No matter the animal, Chapman believes that the sounds could be a conversation. The data was recorded by an acoustic antenna, an array of hydrophones that was towed behind a ship. The uniqueness of the antenna allowed the researchers to identify the direction the sounds were coming from.
“We discovered that there were usually several different speakers at different places in the ocean, and all of them making these sounds,” Chapman said. “The most amazing thing was that when one speaker was talking, the others were quiet, as though they were listening. Then the first speaker would stop talking and listen to responses from others.”
He will present the waveform and spectrum of the recordings during his session, as well as further evidence that the work was a conversation between multiple animals.
“It’s always been an unanswered issue in my mind,” Chapman said. “Maybe they were talking about dinner, maybe it was parents talking to children, or maybe they were simply commenting on that crazy ship that kept going back and forth towing that long string behind it.”
ASA PRESS ROOM In the coming weeks, ASA’s Press Room will be updated with newsworthy stories and the press conference schedule at https://acoustics.org/asa-press-room/.
LAY LANGUAGE PAPERS ASA will also share dozens of lay language papers about topics covered at the conference. Lay language papers are summaries (300-500 words) of presentations written by scientists for a general audience. They will be accompanied by photos, audio, and video. Learn more at https://acoustics.org/lay-language-papers/.
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ABOUT THE ACOUSTICAL SOCIETY OF AMERICA The Acoustical Society of America is the premier international scientific society in acoustics devoted to the science and technology of sound. Its 7,000 members worldwide represent a broad spectrum of the study of acoustics. ASA publications include The Journal of the Acoustical Society of America (the world’s leading journal on acoustics), JASA Express Letters, Proceedings of Meetings on Acoustics, Acoustics Today magazine, books, and standards on acoustics. The society also holds two major scientific meetings each year. See https://acousticalsociety.org/.
Figure 1. Map of 6 underwater acoustic sensing stations of the Comprehensive Test-Ban Treaty Organization.
Figure 4. Trends in annual mean sound pressure level (SPL) from 2006-2021 at Ascension Island at 5 frequency bands: VLF=9-14 Hz; LF=14-28 Hz, MF=28-56 Hz; HF=56-112 Hz; ADEON B = 9-89 Hz. Reproduced with permission from Ainslie, Michael A., et al. “Ocean soundscapes and trends from 2003 to 2021: 10–100 Hz.” The Journal of the Acoustical Society of America 157.6 (2025):4358-4384, Figure 18.
Figure 4. Trends in annual mean sound pressure level (SPL) from 2006-2021 at Ascension Island at 5 frequency bands: VLF=9-14 Hz; LF=14-28 Hz, MF=28-56 Hz; HF=56-112 Hz; ADEON B = 9-89 Hz. Reproduced with permission from Ainslie, Michael A., et al. “Ocean soundscapes and trends from 2003 to 2021: 10–100 Hz.” The Journal of the Acoustical Society of America 157.6 (2025):4358-4384, Figure 18.
A blue whale in the California Current ecosystem. Image Credit: Goldbogen Lab of Stanford University / Duke Marine Robotics and Remote Sensing Lab; NMFS Permit 16111.
