Recommendations on bioacoustical metrics relevant for regulating exposure to anthropogenic underwater sound (PDF)

Klaus, L., A.O. MacGillivray, M.B. Halvorsen, M.A. Ainslie, D. G. Zeddies, and J. A. Sisneros

The Journal of the Acoustical Society of America 156(4): 2508–2526 (2024)

DOI: 10.1121/10.0028586

Metrics to be used in noise impact assessment must integrate the physical acoustic characteristics of the sound field with relevant biology of animals. Several metrics have been established to determine and regulate underwater noise exposure to aquatic fauna. However, recent advances in understanding cause-effect relationships indicate that additional metrics are needed to fully describe and quantify the impact of sound fields on aquatic fauna. Existing regulations have primarily focused on marine mammals and are based on the dichotomy of sound types as being either impulsive or non-impulsive. This classification of sound types, however, is overly simplistic and insufficient for adequate impact assessments of sound on animals. It is recommended that the definition of impulsiveness be refined by incorporating kurtosis as an additional parameter and applying an appropriate conversion factor. Auditory frequency weighting functions, which scale the importance of particular sound frequencies to account for an animal's sensitivity to those frequencies, should be applied. Minimum phase filters are recommended for calculating weighted sound pressure. Temporal observation windows should be reported as signal duration influences its detectability by animals. Acknowledging that auditory integration time differs across species and is frequency dependent, standardized temporal integration windows are proposed for various signal types.

Source and propagation modelling scenarios for environmental impact assessment: Model verification (PDF)

Ainslie, M. A., R.M. Laws, M.J. Smith, A.O. MacGillivray

The Journal of the Acoustical Society of America 156(3): 1489–1508 (2024)

DOI: 10.1121/10.0028135

Evaluation of possible effects of underwater sound on aquatic life requires quantification of the sound field. A marine sound source and propagation modelling workshop took place in June 2022, whose objectives were to facilitate the evaluation of source and propagation models and to identify relevant metrics for environmental impact assessment. The scope of the workshop included model verification (model-model comparison) and model validation (model-measurement comparison) for multiple sources, including airguns, a low-frequency multi-beam echo sounder, and a surface vessel. Several verification scenarios were specified for the workshop; these are described herein.

Modeling the underwater sound of floating offshore windfarms in the Central Mediterranean Sea (PDF)

Baldachini, M., R.D.J. Burns, G. Buscaino, E. Papale, R. Racca, M.A. Wood, and F. Pace

Journal of Marine Science and Engineering 12(9): 1495 (2024)

DOI: 10.3390/jmse12091495

In the shift toward sustainable energy production, offshore wind power has experienced notable expansion. Several projects to install floating offshore wind farms in European waters, ranging from a few to hundreds of turbines, are currently in the planning stage. The underwater operational sound generated by these floating turbines has the potential to affect marine ecosystems, although the extent of this impact remains underexplored. This study models the sound radiated by three planned floating wind farms in the Strait of Sicily (Italy), an area of significant interest for such developments. These wind farms vary in size (from 250 MW to 2800 MW) and environmental characteristics, including bathymetry and seabed substrates. Propagation losses were modeled in one-third-octave bands using JASCO Applied Sciences’ Marine Operations Noise Model, which is based on the parabolic equation method, combined with the BELLHOP beam-tracing model. Two sound speed profiles, corresponding to winter and summer, were applied to simulate seasonal variations in sound propagation. Additionally, sound from an offshore supply ship was incorporated with one of these wind farms to simulate maintenance operations. Results indicate that sound from operating wind farms could reach a broadband sound pressure level (Lp) of 100 dB re 1 µPa as far as 67 km from the wind farm. Nevertheless, this sound level is generally lower than the ambient sound in areas with intense shipping traffic. The findings are discussed in relation to local background sound levels and current guidelines and regulations. The implications for environmental management include the need for comprehensive monitoring and mitigation strategies to protect marine ecosystems from potential acoustic disturbances.

Regional soundscape modeling of the Atlantic Outer Continental Shelf (PDF)

Heaney, K.D., M. Ainslie, J. Murray, A.J. Heaney, J. Miksis-Olds, B. Martin

The Journal of the Acoustical Society of America 156, 378-390 (2024)

DOI: 10.1121/10.0026476

The ocean soundscape is a complex superposition of sound from natural and anthropogenic sources. Recent advances in acoustic remote sensing and marine bioacoustics have highlighted how animals use their soundscape and how the background sound levels are influenced by human activities. In this paper, developments in computational ocean acoustics, remote sensing, and oceanographic modeling are combined to generate modelled sound fields at multiple scales in time and space. Source mechanisms include surface shipping, surface wind, and wave fields. A basin scale model is presented and applied to the United States Atlantic Outer Continental Shelf (OCS). For model-data comparison at a single hydrophone location, the model is run for a single receiver position. Environmental and source model uncertainty is included in the site-specific modeling of the soundscape. An inversion of the local sediment type is made for a set of sites in the OCS. After performing this inversion, the qualitative comparison of the modelled sound pressure level (SPL) time series and observed SPL is excellent. The quantitative differences in the mean root mean square error between the model and data is less than 3 dB for most sites and frequencies above 90 Hz.

Three-dimensional modelling of underwater noise produced by a bulk carrier vessel and estimation of its environmental impact (PDF)

Petrov, S.P, A.G. Tyshchenko, and A.O. MacGillivray

The Journal of the Acoustical Society of America 155 (6): 3702–3714 (2024)

DOI: 10.1121/10.0026238

This study presents the results of three-dimensional (3D) propagation modeling of noise from a transiting bulk carrier vessel. In the simulated scenario, the surface vessel is moving past a bottom-mounted hydrophone system. Sound levels are estimated in decidecade frequency bands as the vessel transits past the hydrophone, and the simulation results are compared against real measured data. The modelling is performed using the program AMPLE, which is based on the wide-angle mode parabolic equation theory for simulating 3D broadband acoustic fields in a shallow sea. The model is used to investigate the effect of 3D phenomena on the surface vessel sound propagation. It is shown that an inaccuracy of the noise simulation associated with the use of a two-dimensional model can be as high as 7–10 dB for certain distances and for frequency bands over which a major part of the source energy is distributed. An approach to the selection of data-adjusted media parameters based on the Bayesian optimization is suggested, and the influence of the various parameters on the sound levels is discussed.

Acoustic occurrence of beaked whales off eastern Canada, 2015–2017 (PDF)

Delarue, J.J.-Y., H.B. Moors-Murphy, K.A. Kowarski, E.E. Maxner, G.E. Davis, J.E. Stanistreet, and S.B. Martin

Endangered Species Research 53: 439–466 (2024)

DOI: 10.3354/esr01314.

Several beaked whale species occur off eastern Canada. However, except for the northern bottlenose whale (NBW; Hyperoodon ampullatus), their distribution and annual occurrence remain largely unknown, which complicates management efforts to assess the status of poorly known species and effectively protect those species considered at risk. The main objective of this paper is to provide a year-round and pluriannual description of the minimum acoustic occurrence of the NBW, Sowerby’s (SBW; Mesoplodon bidens), Cuvier’s (CBW; Ziphius cavirostris), True’s (TBW; M. mirus) and Gervais’ (GBW; M. europaeus) beaked whales. Twenty-five acoustic recorders were deployed off eastern Canada between May 2015 and November 2017. Beaked whale echolocation clicks were detected using a combination of automated detectors and manual validation at 12 of these stations. Detections were generally restricted to deep continental slope waters. All detected species occurred in the southern part of the study area (off the Scotian Shelf and southern Grand Banks), while only NBWs were detected at the northern edge, off southern Labrador. Clicks identified as TBW or GBW were restricted to, but occurred annually in, the southern areas. All other species were present, at least seasonally, east and north of the Grand Banks. NBWs occurred every day in the Gully Canyon, where SBWs also occurred regularly. While these results should be interpreted as minimum species presence and considered with regards to detector performance, they provide important information regarding beaked whales’ use of areas off eastern Canada where these species have generally received no or very limited monitoring effort.

Mapping past and future shipping noise in European seas (PDF)

Recca, R., M.A. Ainslie, J. Bosschers, M. Hermans, T. Lloyd, A.O. MacGillivray, F. Pace, M. Schuster, O. Sertlek and M. Wood

The Journal of the Acoustical Society of America 155, A199 (2024)

DOI: 10.1121/10.0027298

Against the backdrop of a steadily increasing demand for sea transport of goods and people, the development of a reliable marine shipping soundscape model is an essential planning requirement to assess the effect on ocean noise of operational and technological changes aimed at mitigating the environmental impact of the shipping sector. The NAVISON (Navis Sonus) project, conducted with the support of the European Maritime Safety Agency, employs a specially developed parametric vessel source model with the objective of producing shipping sound maps in European seas for past, present, and potential future conditions over a time span from 2016 to 2050. The source model is combined with historical ship tracking data from the automated identification system (AIS), or projected shipping densities and mitigation scenarios, to calculate spatial ship noise emissions data for input to a sound mapping tool. The mapping tool computes underwater sound propagation using the parabolic-equation method, drawing upon ocean-scale databases of bathymetric, oceanographic, and sediment properties. Project outputs are provided as map layers of sound pressure level and sound energy according to vessel type, season, region, year, and operational conditions; from these layers, maps can be generated for user-specified combinations of mitigation measures. Maps are presented in two frequency bands (centred at 63 Hz and 125 Hz) selected for assessing Good Environmental Status in the context of the European Union’s Marine Strategy Framework Directive.

Source level of wind-generated ambient sound in the ocean (PDF)

Chapman, N.R., M.A. Ainslie, M. Siderius

JASA Express Letter 4, 010001 (2024)

DOI: 10.1121/10.0024517

Inference of source levels for ambient ocean sound from local wind at the sea surface requires an assumption about the nature of the sound source. Depending upon the assumptions made about the nature of the sound source, whether monopole or dipole distributions, the estimated source levels from different research groups are different by several decibels over the frequency band 10–350 Hz. This paper revisits the research issues of source level of local wind-generated sound and shows that the differences in estimated source levels can be understood through a simple analysis of the source assumptions.

Soundscape of the Northeast Pacific Ocean revisited (PDF)

Ainslie, M.A. , R.K. Andrew, P.L. Tyack , M.B. Halvorsen , J.M. Eickmeier , A.O. MacGillivray , S.L. Nedelec , and S.P. Robinson

The Effects of Noise on Aquatic Life (2024)

DOI: 10.1007/978-3-031-50256-9_2

The measured changes in northeast (NE) Pacific Ocean ambient sound levels in the 63–125 Hz bands are explained by the contribution from shipping to the sound energy budget using a globally averaged sound energy model. The energy model fails to identify the dominant source of sound in the 32 and 40 Hz bands because its estimates deviate from the measured levels. More research is required to resolve this discrepancy. Ships in cold deep water contribute more to ambient sound than in warm shallow water. This suggests a potential mitigation action for the NE Pacific Ocean.

Ship source measurement in shallow water using an enhanced seabed critical angle method (PDF)

Ainslie, M.A., A.O. Macgillivray, R. Yubero, C.D. Jong, L.S. Wang

DOI: 10.25144/22249

Distant ships are a dominant source of ambient underwater sound at low frequency (50–100 Hz),1, 2 while nearby ships can cause disturbance at frequencies of multiple kilohertz.3 Measurement of a ship’s source level (SL) is needed for soundscape prediction, for quiet ship certification and for validation of prediction models. An international measurement standard exists for the determination of SL using deep water measurements (ISO 17208-24). A draft international standard (DIS) for measuring SL in shallow water, currently under development (ISO/DIS 17208-35), needs an SL formula that is both accurate and straightforward to implement.

Impulsive or non-impulsive: Determining hearing loss thresholds for marine mammals (PDF)

Zeddies, D.G., S.L. Denes, K. Lucke, S. B. Martin, and M.A. Ainslie

The Effects of Noise on Aquatic Life (2023)

DOI: 10.1007/978-3-031-10417-6_188-1

It is well known that short loud sounds and longer quieter sounds can produce hearing loss. The idea that equivalent sound energy results in equivalent hearing loss founds our thinking about hearing loss, including regulations to protect hearing (e.g., NIOSH 1998). But it is also recognized that similar level sounds with different temporal characteristics may result in different amounts of hearing loss. This is codified for regulatory purposes (e.g., NMFS 2018) as lower thresholds for predicting hearing loss in marine mammals exposed to impulsive sounds compared to non-impulsive sounds. Currently, a qualitative approach is used to classify sound sources, which is problematic because sources can produce various sounds, some sources do not neatly fit into either category, and sound characteristics change with propagation.

Kurtosis is a measure of the probability distribution of received sound levels. For hearing, kurtosis appears to better predict hearing loss from exposure to some sounds with differing amounts of transients. The kurtosis of a signal can be used to adjust the received level, allowing for a smooth transition between impulsive and non-impulsive sounds. The adjustment focuses on sounds instead of sources, allows for the consideration of propagation effects, and includes the animals’ hearing frequency sensitivity.

Modelling sound particle motion in shallow water (PDF)

Oppeneer, V.O., C.A.F. de Jong, B. Binnerts, M.A. Wood, and M.A. Ainslie

The Journal of the Acoustical Society of America 154, 4004–4015 (2023)

DOI: 10.1121/10.0022576

Fish species and aquatic invertebrates are sensitive to underwater sound particle motion. Studies on the impact of sound on marine life would benefit from sound particle motion models. Benchmark cases and solutions are proposed for the selection and verification of appropriate models. These include a range-independent environment, with and without shear in the sediment, and a range-dependent environment, without sediment shear. Analysis of the acoustic impedance illustrates that sound particle velocity can be directly estimated from the sound pressure field in shallow water scenarios, except at distances within one wavelength of the source, or a few water depths at frequencies where the wavelength exceeds the water depth.

Multidimensional comparison of underwater soundscapes using the soundscape code (PDF)

Wilford, D.C., J.L. Miksis, and S.B. Martin

Advances in Soundscape: Emerging Trends and Challenges in Research and Practice 154(5): 3438–3453 (2023)

DOI: 10.1121/10.0022514

The soundscape of a given habitat is a product of its physical environment, human activity, and presence of soniferous marine life, which can be used to understand ecosystem processes, habitat quality, and biodiversity. Shallow coral habitats are hotspots of biodiversity and marine life. Deep-sea coral environments, in comparison, are generally poorly understood. Four soundscapes along the U.S. Outer Continental Shelf (OCS) and one soundscape from the Great Barrier Reef were quantified to explore how differences in habitat, depth, and substrate manifest acoustically. Comparisons were made between (1) deep, cold-water and shallow, warm-water coral reefs and (2) deep-sea coral and sandy bottom habitats. Application of the soundscape code to recordings in each location seeded cluster analyses of soundscape metrics and an assessment of daily trends to quantitatively compare the soundscapes. The shallow, tropical reef soundscape differed from the deep-sea soundscapes in amplitude and impulsiveness. Differences in soundscape properties among the deep-sea soundscapes suggested cold-water coral sites produce different soundscapes than the deep sites without live hard bottom. This initial assessment of deep-sea soundscapes along the U.S. OCS provides baseline acoustic properties in a region likely to experience changes due to climate and human use.

Alignment and incentivization of underwater noise notations for quiet ships (PDF)

Trounce, K., M.A.  Ainslie, D. Hannay, and J. Eickmeier

The Effects of Noise on Aquatic Life (2023)

DOI: 10.1007/978-3-031-10417-6_168-1

The approaches for measurement and analysis of underwater vessel radiated noise are complex and evolving. As underwater noise gains increased attention internationally, ship owners and operators are faced with the challenge of understanding the noise emissions of their fleet. An owner seeking to determine if an existing or future vessel design may qualify for a quiet notation must carefully evaluate the available certification options and consider the cost. Differences in terminology, methodology, and approach from international ship classification societies, coupled with the lack of a standardized approach for vessel measurements in shallow water, can make certification daunting to the owner. Recognizing this challenge, the Enhancing Cetacean Habitat and Observation (ECHO) Program led by the Vancouver Fraser Port Authority, supported by Transport Canada, initiated a project to work with ship classification societies and technical experts toward the alignment of quiet ship notations, through a series of three annual workshops. In 2017, Vancouver became the first port in the world to offer financial incentives to ships with quiet notations, and through the alignment project, strives to increase the number of ships achieving notations and being rewarded for this practice – at the Port of Vancouver and around the world.

Estimating the motion parameters of sound sources using a network of compact arrays (PDF)

Urazghildiiev, I.R

IEEE Journal of Oceanic Engineering 48(4): 1270–1279 (2023)

DOI:  10.1109/JOE.2023.3288975

In this article, the problem of employing passive acoustics to estimate the position, speed, and heading angle of a moving source using a network of underwater compact arrays is considered. Maximum-likelihood (ML) estimators using angle-of-arrival (AOA), time-difference-of-arrival (TDOA), and a combination of AOA/TDOA estimates are developed. The estimation accuracy provided by the AOA-based, TDOA-based, and hybrid estimators is evaluated using Cramér–Rao bounds (CRB), statistical simulations, and an in situ test. Test results demonstrate that practical accuracy provided by the proposed algorithms strongly depends on deviations in speed and heading angles from their average values.

Anatomical measurements of dugong auditory systems for evoked potential studies (PDF)

Ketten, D.R., K. Lucke, and J. M. Lanyon

The Effects of Noise on Aquatic Life (2024)

DOI: 10.1007/978-3-031-10417-6_77-1

Dugongs (Dugong dugon) are listed globally as “Vulnerable to Extinction,” raising substantial concerns for their welfare. Underwater sounds are potentially critical survival cues for dugongs, but there are few data on dugong hearing, much less on how ambient sounds, natural or anthropogenic, may affect dugongs.

A project was undertaken in 2022 to obtain auditory evoked potential (AEP) responses in wild Australian dugongs during health assessments. In support of that study, a parallel effort investigated cranial and auditory system anatomy of dugongs to determine optimal placements of hydrophones for delivering sound stimuli and of the recording electrodes for AEP response measurements. Relevant anatomical measurements were obtained from computerized tomography (CT) imaging and dissection of three dugong specimens collected in a previous study of stranded dugongs from northern Australia in collaboration with Dr. Helene Marsh and Dr. Donna Kwan of James Cook University.

The study demonstrated three external landmarks that allow triangulation of surface points closest to the middle ear, inner ear, auditory nerve, and brainstem of dugongs. These anatomical landmarks are proportionately spaced across animals, allowing placement calculations for animals tested in field studies regardless of body mass, age, and sex.

Measuring hearing sensitivity of wild Dugongs in Moreton Bay, Australia (PDF)

Lucke, K., J.M. Lanyon, and D.R. Ketten

The Effects of Noise on Aquatic Life (2024)

DOI: 10.1007/978-3-031-10417-6_94-1

A pilot study to measure hearing capabilities in wild dugongs (Dugong dugon) was conducted in Moreton Bay, Australia. To successfully obtain hearing measurements, an approach for measuring auditory responses in wild dugongs using neurophysiological measures was developed. Preparatory to the measurements, basic head anatomy of dugongs was investigated to optimize placements of the acoustic transmitting and receiving neuronal sensors. Three dugongs were selected as suitable candidates for the auditory measurements based on the results of a preliminary health assessment. Following the absence of observable responses by the first animal, click and sinusoidally amplitude modulated signals were used as acoustic stimuli for the second and third animals, eventually resulting in reproduceable and scalable neuronal responses. The recorded neuronal signals represent a proof of concept for the first auditory measurement in wild dugongs. Valuable insights were gathered during the pilot study allowing optimization of the procedure for a planned follow-up study which will test a larger number of wild dugongs.

Observed transmissions and ocean-ice-acoustic coupled modelling in the Beaufort Sea (PDF)

Barchay, D.R., S.B. Martin, P.C., Hines, J.M. Hamilton, M. Zykov, T. Deveau, P. Borys

The Journal of the Acoustical Society of America 154, 28-47 (2023)

DOI: 10.1121/10.0019942

An ocean-ice-acoustic coupled model is configured for the Beaufort Sea. The model uses outputs from a data assimilating global scale ice-ocean-atmosphere forecast to drive a bimodal roughness algorithm for generating a realistic ice canopy. The resulting range-dependent ice cover obeys observed roughness, keel number density, depth, and slope, and floe size statistics. The ice is inserted into a parabolic equation acoustic propagation model as a near-zero impedance fluid layer along with a model defined range-dependent sound speed profile. Year-long observations of transmissions at 35 Hz from the Coordinated Arctic Acoustic Thermometry Experiment and 925 Hz from the Arctic Mobile Observing System source were recorded over the winter of 2019–2020 on a free-drifting, eight-element vertical line array designed to vertically span the Beaufort duct. The ocean-ice-acoustic coupled model predicts receive levels that reasonably agree with the measurements over propagation ranges of 30–800 km. At 925 Hz, seasonal and sub-seasonal ocean and ice driven variations of propagation loss are captured in the data and reproduced in the model.

On definitions of signal duration, evaluated on close-rangeairgun signals (PDF)

Muller J. A., R, M. A. Ainslie, and M. B. Halvorsen

DOI: 10.1121/10.0019747

Journal of the Acoustical Society of America 153, 3513–3521 (2023)

In impact assessments for underwater noise, the duration of a transient signal is often expressed by the 90%-energy signal duration s90%. Consequently, the rms sound pressure is computed over this duration. Using a large set of measurements on marine-seismic airgun signals, it is shown that s90% is often very close to the interval between the primary and secondary pulse (the bubble period) or a small integer multiple thereof. In this situation s90% is a measure of the duration of the relative silence between primary and secondary peaks, which is not the intended measure. Rarely, s90% quantifies the duration of the main peak, leading to a much lower value of s90%. Since the number of peaks included in s90% is sensitive to the nature of the signal, relatively small differences in the signal lead to large differences in s90%, causing instability in any metric based on s90%, e.g., the rms sound pressure. Alternative metrics are proposed that do not exhibit these weaknesses. The consequences for the interpretation of sound pressure level of a transient signal, and the benefits of using a more stable metric than s90% are demonstrated. VC 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license.

Impact of mobile offshore drilling units on Odontocetes (PDF)

Martin, S.B., K.A. Kowarski, and J.J.-Y. Delarue

The Effects of Noise on Aquatic Life (2023)

DOI: 10.1007/978-3-031-10417-6_103-1

Anthropogenic sounds can negatively impact marine mammals, limiting their ability to effectively forage or communicate, displacing them from a portion of their range, or causing physical harm. To date, potential impacts of sounds associated with mobile offshore drilling units (MODUs) on cetaceans have not been investigated. Acoustic recordings were collected at 1–2 km and 20–40 km from three MODUs to investigate variation in the acoustic occurrence of odontocetes with distance from the MODUs.

The West Aquarius MODU, West Hercules MODU, and Stena Forth MODU acoustic measurements lasted for at least 2 months each and included at least 1 min in 20 with high enough sampling rates to record the echolocation clicks of delphinids, beaked whales, and sperm whales. Recordings in the general area of the operations from previous years were also available. A comparison of the odontocete acoustic presence near the operations to the acoustic presence at longer distances showed a substantial difference in acoustic occurrence for dolphins, pilot whales, and beaked whales that could not be attributed to masking of detections by sounds from the operations.