Collaborating for Conservation: A Summary of Current and Future Directions in Blue Whale Science

Capri D. Joliffe, K. Edyvane, G. Genty, R. D. McCauley, C. McPherson, D. Barlow, B. L. Southall, L. Irvine, T. A. Branch, C. Jenner, M. Jenner, C. Burton, G. Whittome, P. Gill, G. Russell, B. Elsdon, J. Quintas

Aquatic Conservation: Marine and Freshwater Ecosystems (2026)

DOI: 10.1002/aqc.70331

The blue whale has been the focus of considerable research effort worldwide, yet significant gaps remain in the understanding of this species' ecology, behaviour, distribution and resilience to anthropogenic pressures. This review synthesizes insights from an international workshop held during the 25th Biennial Conference on the Biology of Marine Mammals 2024 hosted in Perth, Western Australia, which convened over 40 scientists specializing in blue whale research. The workshop aimed to consolidate the current state of knowledge, identify key research gaps and develop collaborative strategies to advance blue whale science with a focus on the local population of blue whales, the eastern Indian Ocean pygmy blue (EIOPB) whale. With research efforts into the species intensifying in recent years, there exist considerable opportunities for collaboration across research groups to avoid unnecessary duplication of effort and maximize the value of research efforts. Further, filling critical knowledge gaps that limit conservation and effective population management will require holistic studies focused not only on blue whales but on their prey species, krill and the mechanistic links between environmental drivers, krill and blue whales.

Estimating sediment properties using a new source level function for wind-driven underwater sound derived from long-term archival data (PDF)

Martin, S.B. and M. Siderius.

The Journal of the Acoustical Society of America 159(1): 300–314 (2026)

DOI:10.1121/10.0042217

Wind-driven breaking waves generate the background sound throughout the ocean. An accurate source level for wind-driven breaking waves is needed for estimating the ambient sound levels needed for sound exposure modeling, environmental assessments, and assessing the detection performance of sonars. Previous models applied a constant roll-off of sound levels at −16 dB/decade at all wind speeds, and these models' source levels were flat at frequencies below ∼1000 Hz due to a lack of measurements. Here, we analyzed 16 long-term archival datasets with limited anthropogenic sound sources to estimate the wind-driven source level down to 100 Hz. We estimated the site-specific areic propagation loss (APL) using a ray-based model and then added the APL to the median received levels at each wind speed to obtain the source level. An equation for the areic dipole source level is provided that increases as wind speed cubed, like most other air-ocean coupling processes. The model may be used to estimate sediment properties (given a wind speed history and measured sound levels) or to estimate wind speeds (given the sediment type and measured sound levels). It is well suited for estimating ambient sound levels from wind for soundscape modeling. An open-source implementation is available.

Origins of natural and anthropogenic sounds in a coastal, seasonally ice-covered, Antarctic marine soundscape (PDF)

Van Den Hoff, J., J. Delarue, V.E. Warren, C. McPherson, J.L. Lieser, H. Achurch, P. Virtue, and B.S. Miller

Marine Ecology Progress Series 757:17-36(2025)

DOI: 10.3354/meps14813

Baseline characterisation of the acoustic underwater environment is integral to understanding changes in the soundscape of a location. We used passive acoustic monitoring to investigate the soundscape of a seasonally ice-covered, shallow marine environment close to a permanently occupied research station in Prydz Bay, East Antarctica, from July (winter ice cover) 2021 through to February (summer open water) 2022. We applied a suite of automated detectors to detect sounds, with manual analysis of a subset of recordings to validate automated detections and characterise detector performance. From July until late November, the landfast ice cover had a dampening effect on mean daily ambient underwater sound pressure levels. The anthropophony of the ice-covered environment included contributions from aircraft landings and the movements of over-ice vehicles. The biophony was most influenced by the sounds of Weddell, crabeater and leopard seals and Antarctic minke whales. Mean daily sound levels increased immediately as the ice cover decreased and the sea surface became exposed to the effects of wind. The soundscape of the open-water/drifting pack-ice environment then altered to include noise from ship and small boat activities and vocalisations of killer whales and leopard and Ross seals. The results demonstrate a study site with high seasonality in natural sound sources and an unprecedented contribution of noise from human activities during the period of ice cover. There is likely a year-round contribution of anthropogenic noise to the Antarctic coastal marine environment close to research stations that are often co-located with regional hot-spots in faunal occurrences.

A new era for underwater noise impact prediction and management (PDF)

Capri D. Joliffe

Acoustics 2025 — Sounds of the Sunset Coast, Joondalup, Western Australia (2025)

AAS2025/papers/p85

There is global consensus that anthropogenic underwater noise represents a ubiquitous pressure to marine fauna, with an increasing number of studies seeking to understand both the short- and longterm impact of noise exposure on various species. As our understanding of the full extent of threats and pressure to marine fauna populations grows, so too does concern regarding the impacts and management of noise generating activities from offshore industries. Regulators, proponent and EIA practitioners for offshore industries are faced with the challenge of integrating new scientific understandings and increasingly complex impact prediction tools within existing regulatory and management frameworks. Often these management frameworks are based around standardised mitigation measures and set and forget management approaches. These frameworks are limited in their ability to be adaptable to real time information, and often blind to the nuances of operational and environmental context. While the level of environmental impact that is acceptable will vary between environmental and regulatory contexts, EIA and mitigation approaches are often based around demonstrating that impacts are reduced to a level that is as low as practicable and fail to demonstrate that impacts will be managed to achieve a specific environmental outcome. Over the past decade, the technical capability surrounding noise impact prediction has significantly evolved, this has occurred alongside a growing body of information to inform species distribution and habitat use. As our ability to predict the impacts and risks of underwater noise grows, it becomes increasingly evident that set and forget mitigation measures fall short in managing impacts to an acceptable level. This highlights the need for pragmatic underwater noise management frameworks that are sensitive to environmental and operational context and adaptive in their implementation. This paper will discuss best practices in underwater noise impact 

Underwater noise from on-land blasting (PDF)

Quijano, J.E. and M.W. Koessler

JASA Express Letters 5(11): 113601 (2025)

DOI: 10.1121/10.0039805

The production of underwater noise from on-land detonations is of concern, especially near sensitive marine mammal habitats. Despite this, there is a lack of public experimental data to analyze the characteristics of this type of noise. This paper quantifies noise from near-water land detonations, based on measurements obtained at Bentinck Island Demolition Range, Vancouver Island. The measurements show that ground-to-water propagation is dominant and that air-to-water coupling via evanescent waves is also present but mostly perceptible only at close distances from the detonation. A simple wavenumber integration model is used to illustrate the depth dependency of the evanescent field.

Fractional octave and fractional decade frequency bands in acoustics: Historical review and recommendations

Ainslie, M.A., S.P. Robinson, and R. Barham

The Journal of the Acoustical Society of America 158, 3631–3644 (2025)

DOI: 10.1121/10.0039684

Frequency bands are used in acoustical analysis to group sound energy into meaningful bands that simplify frequency-dependent behavior or characterize the spectrum in a manner relevant to the perception of sound. Early frequency bands were typically based on the octave (oct) and submultiples, such as one-third of an octave (1/3 oct), and such base 2 bands were first standardized in the 1950s. Ten 1/3 oct bands span a frequency range close to 1 decade (dec), which made it convenient to divide each decade into ten equal parts, resulting in the specification of 1/10 dec (decidecade) bands by modern standards, replacing the previous 1/3 oct bands. Because 1/10 dec is approximately equal to 1/3 oct, these decidecade bands are sometimes referred to as “one-third octave” bands, even in international standards, leading to ambiguity. The historical evolution of frequency bands in acoustics is reviewed and it is proposed to distinguish clearly between 1 oct and 3/10 dec (or equivalently between one-third of an octave and one-tenth of a decade).

Environmental drivers of foraging by deep-diving cetaceans: Roles of mesoscale oceanography and light-driven cycles (PDF)

Clay, T.A., G. Carroll, M.A. Cimino, J.L. Miksis-Olds, K.A. Kowarski, A.P. Lyons, P.I. Miller, T.S. Moore, J.D. Warren, E.L. Hazen.

Progress in Oceanography Vol.239, 2025

DOI: 10.1016/j.pocean.2025.103581

Foraging by deep-diving marine predators is shaped by the interplay between oceanographic features and light-driven (diel and lunar) cycles that structure the three-dimensional distributions of their mesopelagic prey. While mesoscale features such as fronts and eddies are important for epipelagic predators, their role in driving the foraging behaviour of deep-divers remains poorly understood. We investigated bio-physical drivers of habitat use for dwarf and pygmy sperm whales Kogia spp. and beaked whales Mesoplodon spp. using three years of passive acoustic monitoring at seven sites on the Outer Continental Shelf of the northwest Atlantic Ocean. We analysed acoustic detections alongside satellite- and model-derived oceanographic variables spanning meso- and seasonal scales, and diel and lunar cycles. The two deepest sites, on the Blake Plateau (870 m) and the outer continental slope (790 m), emerged as foraging hotspots with year-round vocal presence of kogiid and beaked whales. Mesoscale activity associated with the Gulf Stream – including current strength and eddy kinetic energy – were foraging predictors, alongside sea surface temperature and primary productivity. However, site-specific habitat models explained only 3–37 % deviance. Blainville’s beaked whale M. densirostris foraging activity peaked during the full moon, likely due to lunar effects on prey concentrations at depth, while there was no clear diel variation for any detected beaked whale species. In contrast, kogiid foraging activity was elevated around sunrise and sunset. These findings suggest a role of near-surface features such as eddies in addition to light-driven cycles in shaping predator–prey dynamics, even in deep continental slope ecosystems.

A Public Dataset of Annotated Orcinus orca Acoustic Signals for Detection and Ecotype Classification (PDF)

Palmer, K.J., E. Cummings, M.G. Dowd, K. Frasier, F. Frazao, A. Harris, A. Houweling, J. Kanes, O.S. Kirsebom, H. Klinck, H. LeBlond, L. Laturnus, C. Matkin, O. Murphy, H. Myers, D. Olsen, C. O’Neill, B. Padovese, J. Pilkington, L. Quayle, A.R. Vuibert, K. Trounce, S. Vagle, S. Veirs, V. Veirs, J. Wladichuk, J. Wood, T. Yack, H. Yurk, and R. Joy

Scientific Data 12(1): 1137 (2025)

DOI: 10.1038/s41597-025-05281-5

Killer whales (Orcinus orca) exhibit significant ecological and genetic diversity, with three primary sympatric populations in the Northeast Pacific: Resident, Bigg’s (Transient), and Offshore. Each population is characterized by distinct foraging habits, social structures, and vocal repertoires, which complicate accurate monitoring and conservation efforts. This dataset, compiled from diverse sources, provides a comprehensive resource for the detection and classification of killer whale vocalizations. The dataset includes annotated acoustic recordings spanning 11 years from various locations in Alaska, British Columbia, and Washington, collected using multiple hydrophone systems. It addresses the challenge of differentiating killer whale calls from other marine species and environmental noise, including specific instances of confounding signals that may help enhance model robustness. Detailed annotations capture a diverse suite of vocalizations and their associated metadata, facilitating the development of advanced machine learning models for ecological monitoring. This curated dataset aims to improve the accuracy of killer whale detection algorithms, support conservation efforts, and advance our understanding of killer whale acoustic communication across different populations.

North Atlantic Right Whale Up-call Localization with a Four-Element Acoustic Array on a Slocum Glider (PDF)

MacGillivray, M., M.L. Seto, S.B. Martin, and L. Bolt

UACE2025

North Atlantic right whales (NARW) are critically endangered, with an estimated 350individuals remaining. Passive acoustic monitoring offers a means to localize the whales, improving the accuracy of exclusion zones to mitigate vessel strikes and fishing entangle ments. This study evaluates multiple time-difference-of-arrival azimuth estimation meth ods for a compact volumetric array (CVA) integrated onto a Slocum glider. The methods tested include minimum difference estimation, k-means clustering, kernel density estimation (KDE), TDoA maximum likelihood estimation, and azigram-KDE estimation. Simulations in a ROS/Gazebo environment, incorporating realistic underwater acoustic conditions, are used to test each of the methods. Verification was achieved with an in-water trial off the coast of Clam Harbour, Nova Scotia, Canada (2024). The NARW upcall is emulated using a moored source producing linear frequency modulated pulses. The trial revealed that the azigram-KDE estimator performed the best, yielding a mean absolute error of 25.6◦ (20.5 % improvement over next best method) and an interquartile range of 10.2◦ (40.7 % improve ment). Successful localization of NARWs with a glider-mounted CVA advances autonomous marine mammal monitoring and supports ongoing conservation efforts.

Ocean soundscapes and trends from 2003 to 2021: 10–100 Hz

Ainslie, M.A., S.P. Robinson, P.M. Harris, P.L. Tyack, M.B. Halvorsen, S.-H. Cheong, V. Livina, and L.-S. Wang

The Journal of the Acoustical Society of America 157, 4358–4384 (2025)

DOI: 10.1121/10.0036831

We analyze ocean ambient sound from a global network of hydrophones installed and maintained by the Comprehensive Nuclear-Test-Ban Treaty Organization. We process acoustic data from nine hydrophones across six hydroacoustic stations distributed across five oceans: North Pacific, South Pacific, South Atlantic, Indian, and Southern oceans, for up to 19 consecutive years between 2003 and 2021. We identify dominant natural and anthropogenic sources for all six stations and observe long-term trends at four of them. Out of 20 statistical tests, 15 identified a significant downward trend in sound pressure level. Possible causes of these decreasing trends include a global recession in 2016, the COVID-19 pandemic in 2020, five major earthquakes between 2004 and 2012 (with none in 2013–2021), and a steadily increasing sea surface temperature, which decreases the sea surface critical angle and hence the contribution from near-surface sources (e.g., shipping) to sound pressure level.

Examining the effect of intensive seismic surveys on abundance and behaviour of groundfish species along a continental slope of Newfoundland and Labrador, Canada

Nguyen, K., J.M. Hanlon, S.B. Martin, P. Borys, D. Schornagel, and C.J. Morris

Marine Pollution Bulletin 215: 117889

DOI:10.1016/j.marpolbul.2025.117889

This study investigated changes in the abundance and behaviour of groundfish species at a relatively deep-water site along the eastern continental slope of Canada, when exposed to a commercial seismic survey that lasted 100 consecutive days. Baited cameras were deployed at control and impact sites, before and after seismic exposure, consisting of 323, 5-h long, videos. Changes in abundance were not explained by seismic surveying noise for any of the five commonly observed fish species. However, Atlantic cod were found to have significantly longer arrival-times to baited camera stations and it took longer for available bait to be consumed immediately after seismic surveying occurred. This effect occurred when fish were exposed to a daily mean sound pressure level >120 dB re 1 μPa2 prior to the experimental measurements. The study contributes towards a better ecological understating of noise-related impacts over a wide range of conditions where groundfish occur.

Long-range propagation of airgun-array signals: Comparing numerical simulations and acoustic recordings in the Ionian sea (PDF)

Affatati, A., F. Pace, M.A. Wood, S. Viola, B.M.P. Galante, V. Sciacca, C. Ducatel, M. Laigle, G. Riccobene, D. Embriaco, F. Simeone, G. Marinaro, F. Romanelli, R. Racca, A. Camerlenghi.

The Journal of the Acoustical Society of America 157, 2857–2867 (2025)

DOI: 10.1121/10.0036457

Marine seismic surveys contribute to acoustic pollution, and the sounds they produce may be audible by marine mammals at several hundred kilometers distance. To evaluate the potential effects of such sounds on fauna and translate them into effective policies and mitigation measures, stakeholders require quantitative estimations of acoustic fields. We compare simulations of airgun-array signals produced during the Upper LIthosphere Ship Subduction Exploration survey in the Ionian Sea with the signals recorded 650 kilometers away at the cabled seabed observatory NEMO-SN1. JASCO's Applied Sciences' Airgun Array Source Model was used to predict the sound levels for two configurations of 18-element airguns, and the signal was then propagated in a realistic environment utilizing JASCO's Full-Waveform Range dependent Acoustic Model from the source to the position of the receiver station. There is a qualitative agreement between the simulated, denoised, and recorded signals of the airgun arrivals. However, the signal simulated at 650 kilometers from the source stretches and shows fewer high-frequency components compared to the received one. Our study quantitatively shows that the peaks produced by a large airgun array during a scientific cruise, at 160–180 Hz are not masked by ambient noise even in busy shipping locations at a distance of 650 km.

Measuring vessel source level in shallow water using the smoothed semi-coherent image method

Yubero, R., C.A.F. de Jong, M.A. Ainslie, A.O. MacGillivray, and L. Wang.

Journal of the Acoustical Society of America 157(3): 1938–1954 (2025)

DOI: 10.1121/10.0036140

Standardizing the process for measuring underwater sound generated by ships in shallow waters is a complex challenge currently under development. Recent progress has enabled the development of analytical formulations to represent propagation conditions underwater using propagation loss (PL) approximations, which are employed to derive the source level (SL) from ship sound pressure level (SPL) measurements. Underwater radiated noise (URN) tests conducted in the SATURN project enabled a detailed evaluation of the seabed critical angle (SCA) method, recommended by an early draft of the ongoing ISO 17208-3 standard, identifying a general underestimation of SL above ∼500 Hz compared to measurements under equivalent operating conditions in deep water, as described by ISO 17208-1. This article presents an alternative smoothed semi-coherent image (SSCI) method for calculating PL (and hence SL) and assesses the method's performance through analytical and empirical scenarios (including recordings of three different instrumentation deployment strategies at four distinct depths and four test distances). The SSCI method enhances accuracy over a broad frequency range while maintaining the general robustness, with a formulation that also seeks to preserve the simplicity of the SCA approach.

We Go Signaling Into the Night: Describing an Echolocation Signal of an Unknown Beaked Whale (Cetacea; Ziphiidae)off West Africa (PDF)

Runte, K.L., K.A. Kowarski, J.J.-Y. Delarue, E.E. Maxner, D. Hedgeland, S.B. Martin

Marine Mammal Science 41(3): e70002 (2025)

DOI: 10.1111/mms.70002

Beaked whales (Cetacea; Ziphiidae), one of the most diverse families of cetaceans, can be identified by species-specific, frequency-modulated echolocation signals. Of the 24 known species of beaked whales, over half have been assigned a unique signal type. A novel echolocation pulse belonging to an unknown beaked whale species was recorded off West Africa (Beaked Whale of West Africa, BWWA), along the coast of the Democratic Republic of São Tomé and Príncipe. Bottom-mounted autonomous acoustic recorders (sampling rate of 375 kHz) were deployed from October 2018 to August 2019 (294 recording days) at depths of 450–600 m. An automated detector-classifier created to identify BWWA (per file Precision of 1.00; Recall of 1.00)-guided manual validation. BWWA was present in all recording months and detected during local nighttime hours (98% of detections occurred during fully dark periods). BWWA had a 52.5 kHz median peak frequency, 55.4 kHz center frequency, 29.0 kHz −10 dB bandwidth, 843 μs duration, and 86 ms inter-pulse interval (IPI). While species identification remains unsolved for BWWA, spectral similarities to unidentified signals in the Pacific Ocean, BWC, and in the Gulf of Mexico, BWG, find that all three signals can be characterized by longer pulse durations and shorter IPIs.

Exploring offshore particle motion soundscapes

Jones, I.T., S.B. Martin, and J.L. Miksis-Olds

The Journal of the Acoustical Society of America 157: 149–168 (2025)

DOI:10.1121/10.0034748

Fishes and aquatic invertebrates utilize acoustic particle motion for hearing, and some additionally detect sound pressure. Yet, few underwater soundscapes studies report particle motion, which is often assumed to scale predictably with pressure in offshore habitats. This relationship does not always exist for low frequencies or near reflective boundaries. This study compared particle motion and sound pressure from hydrophone arrays near the seafloor at six sites on the U.S. Mid and South Atlantic Outer Continental Shelf and assessed predictability of sound pressure and particle motion levels by environmental indicators (wind, vessels, temperature, currents). Unidentified fish sounds (100–750 Hz) had particle motion magnitudes 4.8–12.6 dB greater than those predicted from single hydrophone (pressure) measurements, indicating that these sounds were received in the near field. Excess particle motion attributed to hydrodynamic flow noise (<100 Hz) was also present at all sites. Most sounds (25th–75th percentile) from other sources received in the far field (vessels, mammals), had measured particle motion within ±3 dB of that predicted from single hydrophone measurements. The results emphasize for offshore soundscapes the importance of particle motion measurement for short-time (1 min) and near field signals, and that pressure measurement is sufficient for long-term (1 year) predictive modeling.

Techniques for modeling ocean soundscapes: Detailed description for wind contributions (PDF)

Siderius, M., M.A. Ainslie, J. Gebbie, A. Schafke, N. R. Chapman, S.B. Martin, and K.L. Gemba

The Journal of the Acoustical Society of America 156(5): 3446–3458 (2024)

DOI: 10.1121/10.0034236

Wind over the ocean creates breaking waves that generate air-filled bubbles, which radiate underwater sound. This wind-generated sound is a significant component of the ocean soundscape, and models are essential for understanding and predicting its impact. Models for predicting sound pressure level (SPL) from wind have been studied for many years. However, the terminology and definitions behind modeling approaches have not been unified, and ambiguity has led to differences in predicted SPL. The 2022 Ambient Sound Modeling Workshop was organized to compare ambient sound modeling approaches from different researchers. The main goal of the workshop was to quantify differences in predicted SPL and related quantities for different approaches and, to the extent possible, determine the cause of the differences for a specific, well-defined scenario. Results revealed a variation of approximately 6 dB across different research groups, with differences reaching up to 10 dB in some cases compared to the benchmark results described in this paper. These variations stemmed from differing methodologies and underlying assumptions. In this paper, step-by-step guidance is given for modeling SPL due to wind. The workshop test case will be described, and results from the modeling approaches described here will be compared with those from the workshop participants.

Verifying models of the underwater soundscape from wind and ships with benchmark scenario (PDF)

Martin, S.B., M. Siderius, M.A. Ainslie, M.B. Halvorsen, L. Hatch, M.K. Prior, D. Brooker, J. Caplinger, C. Erbe, J. Gebbie, K. D. Heaney, A.O. MacGillivray, M. Matthews, V.O. Oppeneer, A. Schafke,  R.P. Schoeman, and H.O. Sertlek

The Journal of the Acoustical Society of America 156(5): 3422–3438 (2024)

DOI: 10.1121/10.0026597

Models of the underwater acoustic soundscape are important for evaluating the effects of human generated sounds on marine life. The performance of models can be validated against measurements or verified against each other for consistency. A verification workshop was held to compare models that predict the soundscape from wind and vessels and estimate detection ranges for a submerged target. Eight modeling groups participated in the workshop which predicted sound levels with observation windows of 1 min and 1 km2. Substantial differences were found in how modelers computed the propagation losses for decidecade bands and estimated the source level of wind. Further investigations resulted in recommendations on best practices. Choices of temporal and spatial modeling resolution affected the estimates of metrics proportional to total sound energy more than distributions of sound pressure level. Deeper receivers were less sensitive to these parameters than shallow ones. A temporal resolution of 1 min and spatial resolution of 100 m is recommended. Models that follow the recommendations will yield similar results. The detection range of underwater targets is highly variable when the ambient noise depends on moving noise sources. Future work to verify models against data and understand model uncertainty is recommended.

Subtle shift in depth distribution of fish within the impact range of seismic surveying along a continental slope

Hynes, H., K.Q. Nguyen, M. Geoffroy, S.B. Martin, and C.J. Morris

Canadian Journal of Fisheries and Aquatic Sciences

DOI: 10.1139/cjfas-2025-0027

The impact of an industry-based 3D seismic airgun survey on fish and zooplankton was investigated on offshore commercial fishing grounds in Newfoundland and Labrador. Seismic surveying was conducted for 100 consecutive days during summer 2021. A seabed moored autonomous multichannel acoustic recorder measured sound levels while a wideband autonomous transceiver equipped with 38 and 333 kHz transducers measured fish and zooplankton backscatter in the water column. The distance between the seismic survey vessel and the instruments ranged from 0 to 152 km and was tracked continuously. Fish between depths of 50 and 350 m exhibited a response to seismic surveying, descending to greater depths when the seismic vessel was within 60 km and when average sound pressure levels were >122 dB re 1 μPa2. Conversely, no discernible effect on zooplankton abundance or behavior was measured between 250 and 340 m depths. These findings suggest that the effects of seismic surveying in offshore environments are mainly impacting fish behaviour when sound levels are high, and impacts were observed at greater horizontal distances than previously reported.

Range versus frequency averaging of underwater propagation loss for soundscape modeling (PDF)

Zykov, M.M., and S.B. Martin

The Journal of the Acoustical Society of America 156(5): 3439–3445 (2024)

DOI: 10.1121/10.0030475

Guidance on efficient methods is needed for the practical application of modeling the sound field from broadband sources such as vessels, seismic surveys, and construction activities. These sound field models are employed for estimating how changes in the soundscape will affect marine life. For efficiency, acoustic propagation modeling is often performed in bands (decidecade or 1/3-octave), where propagation loss modeled for central frequency is assumed to represent an average propagation loss in the band. This shortcut comes at the expense of accuracy, which can be rectified by averaging the propagation loss across many frequencies in the band. Alternately, the equivalence of range and frequency averaging was shown by Harrison and Harrison [J. Acoust. Soc. Am. 97, 1314–1317 (1995)]. However, when and how to apply range averaging required further investigations. A simple environment with a flat sandy bottom and an isovelocity water-column sound speed profile was considered to test the agreement between the range and frequency averages for decidecade bands typically considered in soundscape modelling (10–1000 Hz). The optimal range smoothing window is a Gaussian window with a width of 10%–16% of the range from the source that switches to a width fixed beyond 20 km distance from the source.

Sound emissions from Ultrasonic Antifouling equipment (PDF)

Martin, S.B., A.O. MacGillivray, J.D. Wood, K.B. Trounce, D.J. Tollit, K. Angadi

The Effects of Noise on Aquatic Life (2024)

DOI: 10.1007/978-3-031-50256-9_102

The Vancouver-Fraser Port Authority-led Enhanced Cetacean Habitat and Observation (ECHO) Program has managed underwater listening stations (ULSs) on the approach to the Port of Vancouver since 2015, measuring the sound levels generated by thousands of vessels. Since 2017, these systems have measured at or above a 128 kHz sampling rate. Anomalously high sound levels were observed in 212 of the measured ships signatures at frequencies typically associated with navigational, fisheries, and scientific sonars. Sixty-one of these detections were found to originate from a novel continuous sound source in the 20–30 kHz frequency range. During a separate underwater noise monitoring program, a similar high-frequency continuous sound source was identified proximate to a berthed vessel. The vessel engineer identified it as an ultrasonic antifouling system. The sounds from these systems are detectable at 4–6 km from the vessels in deep water. The measurements indicate that echolocation by lower-frequency delphinids, such as killer whales, may be completely masked when a ship is 3 km away and that porpoises flee from the source at distances of 1.5 km. In shallow waters, a porpoise 70 m from the source is predicted to experience temporary threshold shift (TTS) after 1–2 s, and permanent threshold shift (PTS) after 200 s. It is recommended that use of these systems be restricted or prohibited when there is a possibility of exposing marine mammals to potentially harmful sound levels.