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.

Measurements of underwater radiated noise from mobile offshore drilling units (PDF)

Austin, M.E., S.B. Martin, C.R. McPherson

The Effects of Noise on Aquatic Life (2023)

DOI: 10.1007/978-3-031-10417-6_7-1

Mobile offshore drilling units (MODUs) are used to drill oil and gas wells in the ocean. For deeper water operations, there are two common forms of MODUs: semisubmersible rigs and drillships. Over the past several years, JASCO Applied Sciences measured MODU drilling operations by semisubmersibles and drillships, including platforms that were moored with anchors or that held position using dynamic positioning (DP) thrusters. The MODUs were accompanied by support vessels on standby, with additional vessels conducting resupply operations during the drilling campaigns. The measurements were performed in response to regulators requesting verification of the vessel source levels and the distances where the sounds were expected to either injure or disturb marine life.

Overall, drillships had higher source levels than semisubmersibles. Moored platform sound levels decreased with drilling depth and hole diameter. The signatures of moored platforms featured tones from different types of rotating machinery. When platforms or nearby support vessels were holding station using DP, the tonal signatures were obscured by DP thruster sounds. All measurements of underwater radiated noise from platforms using DP contained sounds from ultrashort baseline (USBL) beacons at 25–27 kHz.

Measuring vessel underwater radiated noise in shallow water (PDF)

MacGillivray, A.O., S.B. Martin, M.A. Ainslie, J.N. Dolman, Z. Li, and G.A. Warner

The Journal of the Acoustical Society of America 153, 1506 (2023)

DOI: 10.1121/10.0017433

Performing reproducible vessel source level (SL) measurements is complicated by seabed reflections in shallow water. In deep water, with a hydrophone far from the seabed, it is straightforward to estimate propagation loss (PL) and convert sound pressure level (SPL) into SL using the method codified in the international standard ISO 17208-2 [International Organization for Standardization (ISO), Geneva, Switzerland (2019)]. Estimating PL is more difficult in shallow water because of the way that sound reflects from the seabed such that multiple propagation paths contribute to SPL. Obtaining reproducible SL measurements in shallow water requires straightforward and robust methods to estimate PL. From May to July 2021, a field experiment evaluated different methods of measuring vessel SL in shallow water. The same vessels were measured many times in water depths of 30, 70, and 180 m. In total, 12 079 SL measurements were obtained from 1880 vessel transits and 16 hydrophones, distributed across 3 moored vertical line arrays and 2 moored horizontal line arrays. The experiment confirmed that it is possible to obtain reproducible vessel SL estimates in shallow water comparable to within ±2.5 dB of ISO-compliant measurements in deep water and repeatable to within ±1.5 dB.

Vector acoustic properties of underwater noise from impact pile driving measured within the water column (PDF)

Dahl PH, A.O. MacGillivray, and R. Racca

Frontier Marine Science 10:1146095.

DOI: 10.3389/fmars.2023.1146095

Vector acoustic properties of the underwater noise originating from impact pile driving on steel piles has been studied, including the identification of features of Mach wave radiation associated with the radial expansion of the pile upon hammer impact. The data originate from a 2005 study conducted in Puget Sound in the U.S. state of Washington, and were recorded on a four-channel hydrophone system mounted on a tetrahedral frame. The frame system measured the gradient of acoustic pressure in three dimensions (hydrophone separation 0.5 m) from which estimates of kinematic quantities, such as acoustic velocity and acceleration exposure spectral density, were derived. With frame at a depth of 5 m in waters 10 m deep, the data provide an important look at vector acoustic properties from impact pile driving within the water column. Basic features of the Mach wave are observed in both dynamic (pressure) and kinematic measurements, most notably the delay time TT leading to spectral peaks separated in frequency by 1/T∼ 1061/T∼ 106 Hz, where TT equals the travel time of the pile radial deformation over twice the length of the pile. For the two piles studied at range 10 and 16 m, the strike-averaged sound exposure level (SEL) was ∼∼ 177 dB re 1μ1μPa2Pa2-s and the acceleration exposure level (AEL) was 122-123 dB re μμm2m2/s4/s4 s. The study demonstrates an approximate equivalence of observations based on dynamic and kinematic components of the underwater acoustic field from impact pile driving measured within the water column.

Methods to measure underwater sound sources from oil and gas activities (PDF)

De Jong, C.A.F., M.B. Halvorsen, D.E. Hannay, and M. A. Ainslie

The Effects of Noise on Aquatic Life (2023)

DOI: 10.1007/978-3-031-10417-6_37-1

In 2021, the International Association of Oil and Gas Producers (IOGP) published a report in which measurement procedures are described that enable the acoustic characterization of underwater sound sources associated with seismic acquisition, high-resolution geophysical surveys, and production of oil and gas. These procedures are designed to provide consistency and comparability of independently carried out measurements. An initial review of existing methods revealed that there was some commonality in reported measurements of airgun arrays and high-resolution geophysical sources, but very few reports or publications included all relevant parameters. Achieving comparability in measurements requires precise nomenclature and clear documentation of the various choices made concerning measurement geometry, instrumentation, and processing. The measurement procedures describe requirements and recommendations for equipment selection, calibration, placement in depth and range, sampling rates, and operational measurement procedures for the three source types. Signal analysis methods are specified, as well as reporting content and formats for the acoustic results and relevant metadata. Where possible, calculation procedures are described to determine source metrics from the measured acoustic field, which can be used as input for environmental impact assessments for future projects.

Acoustic and visual cetacean surveys reveal year‑round spatial and temporal distributions for multiple species in northern British Columbia, Canada (PDF)

Frouin‑Mouy, H., X. Mouy, J. Pilkington, E. Küsel,L. Nichol, T. Doniol‑Valcroze, and L. Lee

Scientific Reports 12, 19272 (2022).

DOI: 10.1038/s41598-022-22069-4

Cetaceans spend most of their time below the surface of the sea, highlighting the importance of passive acoustic monitoring as a tool to facilitate understanding and mapping their year-round spatial and temporal distributions. To increase our limited knowledge of cetacean acoustic detection patterns for the east and west coasts of Gwaii Haanas, a remote protected area on Haida Gwaii, BC, Canada, acoustic datasets recorded off SG̱ang Gwaay (Sep 2009–May 2011), Gowgaia Slope (Jul 2017–Jul 2019), and Ramsay Island (Aug 2018–Aug 2019) were analyzed. Comparing overlapping periods of visual surveys and acoustic monitoring confirmed presence of 12 cetacean species/species groups within the study region. Seasonal patterns were identified for blue, fin, humpback, grey and sperm whale acoustic signals. Killer whale and delphinid acoustic signals occurred year-round on both coasts of Haida Gwaii and showed strong diel variation. Cuvier’s, Baird’s, beaked whale and porpoise clicks, were identified in high-frequency recordings on the west coast. Correlations between environmental factors, chlorophyll-a and sea surface temperature, and cetacean acoustic occurrence off Gwaii Haanas were also examined. This study is the first to acoustically monitor Gwaii Haanas waters for an extended continuous period and therefore serves as a baseline from which to monitor future changes.

Acoustic monitoring and analyses of air gun, pile driving, vessel, and ambient sounds during the 2015 seismic surveys on the Sakhalin shelf (PDF)

Rutenko, A.N., M.M. Zykov, V.A. Gritsenko, M. Yu. Fershalov, M.R. Jenkerson, D.S. Manulchev, R. Racca, and V.E. Nechayuk

Environmental Monitoring and Assessment 194 (Suppl 1): 744 (2022)

DOI: 10.1007/s10661-022-10021-y

During the summer of 2015, four 4D seismic surveys were conducted on the northeastern Sakhalin shelf near the feeding grounds of the Korean-Okhotsk (western) gray whale (Eschrichtius robustus) population. In addition to the seismic surveys, onshore pile driving activities and vessel operations occurred. Forty autonomous underwater acoustic recorders provided data in the 2 Hz to15 kHz frequency band. Recordings were analyzed to evaluate the characteristics of impulses propagating from the seismic sources. Acoustic metrics analyzed comprised peak sound pressure level (PK), mean square sound pressure level (SPL), sound exposure level (SEL), T100%, T90% (the time intervals that contain the full and 90% of the energy of the impulse), and kurtosis. The impulses analyzed differed significantly due to the variability and complexity of propagation in the shallow water of the northeast Sakhalin shelf. At larger ranges, a seismic precursor propagated in the seabed ahead of the acoustic impulse, and the impulses often interfered with each other, complicating analyses. Additional processing of recordings allowed evaluation and documentation of relevant metrics for pile driving, vessel sounds, and ambient background levels. The computed metrics were used to calibrate acoustic models, generating time resolved estimates of the acoustic levels from seismic surveys, pile driving, and vessel operations on a gray whale distribution grid and along observed gray whale tracks. This paper describes the development of the metrics and the calibrated acoustic models, both of which will be used in work quantifying gray whale behavioral and distribution responses to underwater sounds and to determine whether these observed responses have the potential to impact important parameters at the population level (e.g., reproductive success).

Gray whale density during seismic surveys near their Sakhalin feeding ground (PDF)

Gailey, G., M.M. Zykov, O. Sychenko, A. Rutenko, A.L. Blanchard, L.A.M. Aerts, and R.H. Melton

Environmental Monitoring and Assessment 194 (Suppl 1): 739 (2022)

DOI: 10.1007/s10661-022-10025-8

Oil and gas development off northeastern Sakhalin Island, Russia, has exposed the western gray whale population on their summer-fall foraging grounds to a range of anthropogenic activities, such as pile driving, dredging, pipeline installation, and seismic surveys. In 2015, the number of seismic surveys within a feeding season surpassed the level of the number and duration of previous seismic survey activities known to have occurred close to the gray whales’ feeding ground, with the potential to cause disturbance to their feeding activity. To examine the extent that gray whales were potentially avoiding areas when exposed to seismic and vessel sounds, shore-based teams monitored the abundance and distribution of gray whales from 13 stations that encompassed the known nearshore feeding area. Gray whale density was examined in relation to natural (spatial, temporal, and prey energy) and anthropogenic (cumulative sound exposure from vessel and seismic sounds) explanatory variables using Generalized Additive Models (GAM). Distance from shore, water depth, date, and northing explained a significant amount of variation in gray whale densities. Prey energy from crustaceans, specifically amphipods, isopods, and cumaceans also significantly influenced gray whale densities in the nearshore feeding area. Increasing cumulative exposure to vessel and seismic sounds resulted in both a short- and longer-term decline in gray whale density in an area. This study provides further insights about western gray whale responses to anthropogenic activity in proximity to and within the nearshore feeding area. As the frequency of seismic surveys and other non-oil and gas anthropogenic activity are expected to increase off Sakhalin Island, it is critical to continue to monitor and assess potential impacts on this endangered population of gray whales.