Acoustics and anthropogenic underwater noise in the IWC Scientific Committee (1951–2024): a systematic document review and scientometric synthesis

Anthropogenic underwater noise has become a major environmental and ocean-governance concern affecting marine mammals worldwide, motivating increasing attention within international conservation bodies such as the International Whaling Commission (IWC). Here, we reconstruct how acoustics and anthropogenic underwater noise emerged, expanded, and diversified within the IWC Scientific Committee through a PRISMA-guided document screening combined with scientometric and qualitative classification analyzes. A total of 7,830 Scientific Committee documents produced between 1951 and 2024 were compiled and screened using an automated keyword strategy, yielding 2,949 records for eligibility assessment. Following screening, 644 documents were retained for analysis, encompassing both acoustic-related studies and documents addressing anthropogenic underwater noise as an environmental or management issue. Among these, 594 documents (7.4%) addressed acoustics, spanning 50 years (1962–2024) with a marked increase from the late 1990s onwards. Explicit underwater-noise content was identified in 180 documents (2.16%), first appearing in 1979 and recurring across 38 years, with contributions concentrated in the Environmental Concerns, Small Cetaceans, and Whale Watching subcommittees. Ten standardized sound-source categories were identified, dominated by shipping, seismic surveys, and sonar, while additional sources emerged progressively over time. Reported impacts were primarily behavioral and spatial, whereas auditory damage and mortality were associated with high-intensity sources. Institutional participation was extensive, involving 559 institutions across 75 countries, but remained highly concentrated among a limited number of recurrent contributors. Together, these findings provide the first long-term synthesis of how underwater noise evolved within the Scientific Committee from a specialized acoustic topic into a policy-relevant environmental issue, revealing how scientific knowledge, institutional priorities, and governance discussions co-evolved within the IWC framework.

The physical properties of underwater sound, including efficient propagation over long distances and reduced attenuation compared to light, make it a primary sensory and communication channel for marine animals adapted to aquatic environments. As a consequence of this ecological importance, the rapidly expanding field of marine bioacoustics aims to characterize underwater sound in relation to the acoustic capabilities of particular species (acoustic habitat) and to uncover the role of acoustics in the lives of marine animals (acoustic ecology) (Clark et al., 2011). The field has experienced significant growth in recent years, with numerous studies on the acoustics of marine animals being published (e.g., Andriolo et al., 2018; Erbe et al., 2019; Seger and Miksis-Olds, 2020; Amorim et al., 2022; Fleishman et al., 2023).

Underwater noise pollution can have adverse effects on marine organisms and has been associated with global economic growth (Frisk, 2012). Marine mammals are particularly vulnerable to anthropogenic noise due to their specialized use of sound for communication, navigation, and foraging in aquatic environments (Richardson et al., 1995; Erbe et al., 2018). Underwater noise originates from a wide range of human activities operating across marine environments (Nowacek et al., 2007; Slabbekoorn, 2019; Moretti and Affatati, 2023). Major sources include shipping (Rolland et al., 2012; Erbe et al., 2019), geophysical seismic surveys (Gordon et al., 2003), naval sonar operations (Tyack et al., 2011), offshore construction activities such as pile driving (Huang et al., 2023), and the expansion of marine energy and industrial operations (Tougaard et al., 2009), all of which have been associated with potential effects on marine fauna.

Anthropogenic underwater noise is divided into impulsive and continuous sources (Southall et al., 2007), each producing distinct biological responses and requiring different mitigation and management approaches. Impulsive noise is characterized by short-duration signals with rapid onset and high peak sound levels, such as explosions, pile driving, and seismic air gun pulses, and may cause acute effects including temporary or permanent auditory damage (Southall et al., 2007), physiological stress responses, and behavioral reactions such as avoidance or displacement (Francis and Barber, 2013). Because these activities are typically associated with discrete industrial operations, they are commonly regulated through environmental licensing and operational mitigation requirements (Merchant et al., 2016). In contrast, continuous noise consists of persistent or regularly occurring sounds present over extended periods, mostly generated by commercial shipping. This form of noise has been linked to acoustic masking of biologically relevant signals, disruption of foraging behavior, elevated stress responses, and developmental effects in aquatic organisms (Clark et al., 2009; Erbe et al., 2018; Francis and Barber, 2013). Owing to their continuous operation across large spatial scales and frequent transboundary nature, effective management of these sources requires coordinated international governance frameworks (Francis and Barber, 2013).

Over the past several decades, the impacts of anthropogenic underwater noise on marine animals have gained increasing scientific and regulatory attention (Southall et al., 2007, 2019; Gomez et al., 2016; National Academy of Sciences, 2017) and are now recognized as a global environmental concern. This trend reflects the broader incorporation of marine pollution, including both chemical and acoustic stressors, into international ocean science and policy agendas (Popper and Hawkins, 2019; Ferrier-Pagès et al., 2021; Vakilli et al., 2021; Pichegru et al., 2022). This issue has been addressed in studies and international discussions at the International Maritime Organization (IMO), which has developed guidelines to reduce underwater noise (International Maritime Organization (IMO), 2023), as well as through environmental impact assessments for activities generating marine noise (Convention on Migratory Species (CMS), 2017). Additionally, anthropogenic ocean noise is identified as a priority threat in the Conservation Committee’s Strategic Plan of the International Whaling Commission (IWC). In 2018, the Committee approved further work on anthropogenic underwater noise, including the establishment of an intersessional correspondence group and collaboration with other organizations, reflecting the increasing institutionalization of underwater noise as a conservation issue within the Commission.

Despite the growing recognition of underwater noise within international marine governance, the evolution of this topic within the IWC’s scientific advisory processes has not been comprehensively assessed. Given that IWC Scientific Committee documents are produced within a science–policy interface to inform conservation and management decisions, they also provide a valuable historical record of how emerging scientific issues become incorporated into international environmental governance. Examining how research on acoustics and anthropogenic underwater noise has evolved within this science–policy forum provides an opportunity to explore the relationship between scientific knowledge and institutional responses within the IWC. By analyzing temporal and thematic trends and institutional participation patterns, this study contributes to ongoing discussions on the effectiveness of the science–policy interface in marine mammal conservation.

In this context, we conducted a systematic document review and scientometric analysis of documents submitted to the IWC Scientific Committee addressing acoustics and anthropogenic underwater noise. We reconstructed how these topics emerged, expanded, and diversified over more than seven decades, providing the first long-term synthesis of underwater-noise research within the IWC. This synthesis establishes a historical and institutional baseline for future investigations into the relationship between scientific knowledge, governance, and marine mammal conservation policy.

This study applies a scientometric and qualitative classification approach to documents submitted to the IWC Scientific Committee, with the objective of examining how acoustics and anthropogenic underwater noise have been addressed over time. The analysis focuses on identifying temporal patterns and thematic developments, including the emergence of concerns related to underwater noise, associated sound sources, and assessed impacts. Each document constituted the primary unit of analysis throughout the study.

Document identification and screening

Documents submitted to the IWC Scientific Committee between 2012 and 2024 were obtained directly from the official IWC website, whereas earlier documents (1951–2011) were accessed through direct communication with the IWC, which provided archived materials not publicly available online. Together, these sources ensure coverage of all Scientific Committee meeting documents available in digital format. Archived documents available only as scanned files were converted to machine-readable text using optical character recognition, and the outputs were visually checked to ensure readability prior to automated screening.

The PRISMA framework (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) was adopted to ensure a systematic and transparent document identification and selection process (Tranfield et al., 2003; Moher et al., 2015; Page et al., 2021). PRISMA was applied as a procedural framework to structure document screening rather than to conduct a traditional systematic literature review.

Relevant search terms were identified using the litsearchr package in R (Grames et al., 2019), which applies keyword co-occurrence networks to suggest candidate terms. Selected keywords included acoustic, noise, sound, echolocation, hydrophone, and underwater noise. Automated keyword searches were then conducted across all documents using the pdftools package in R (Ooms, 2023). This screening identified 2,949 documents, which were subsequently subjected to manual eligibility assessment based on predefined inclusion and exclusion criteria (Figure 1).

Documents were included if they (i) addressed acoustics and/or anthropogenic underwater noise as a central focus, either through acoustic methods or explicit treatment of sound as an environmental pressure or impact; (ii) were formally presented at meetings of the IWC Scientific Committee; and (iii) constituted scientific papers, including original studies, reviews, or theoretical or methodological analyzes. The exclusion criteria were (i) documents that did not use acoustics as a research method, did not have acoustics as the primary focus, and/or did not evaluate anthropogenic underwater noise as a causal driver of biological impact or a management concern; (ii) documents that mentioned acoustic- or sound-related terms only in general discussions, secondary references, or citations; (iii) documents consisting of research proposals, budget documents, or administrative materials; or (iv) reports or meeting documents intended primarily to record information from workshops, research projects, or administrative activities without presenting original scientific analyzes. To avoid historical bias associated with the limited availability of early records, an exception to criterion (iv) was applied to the initial period of the IWC Scientific Committee’s activities (the 1960s and 1970s).

Data extraction

Data were extracted directly from each document, including bibliographic and contextual information such as document code, authorship, title, year of publication, and associated IWC Scientific Committee subcommittee or working group. Each document was screened to identify the presence of acoustic research and explicit references to underwater noise as an environmental concern. Information on participating institutions, institutional type, and country affiliation was also extracted to characterize the organizational context of the studies. A single document could contribute multiple entries across variables when more than one institution, country, or thematic element was reported.

When available, descriptions of anthropogenic sound sources were extracted from the original text of each document using the terminology reported by the authors. Because terminology varied among documents and across decades, sources were subsequently standardized through a functional classification approach based on the type of anthropogenic activity generating the sound rather than on the specific terminology used in individual studies.

Sound sources were classified into standardized categories designed to group acoustically and operationally comparable activities. Each reported source was assigned to a single category corresponding to its primary operational origin to ensure consistency and comparability across historical periods of the dataset. This approach allowed sources described using different terms or levels of specificity to be analyzed within a unified analytical framework while preserving the original meaning of the reported activities (Table 1).

Reported impacts associated with underwater noise sources were collected exclusively from explicit descriptions provided in the original documents and grouped into operational categories developed inductively from recurring response types identified during data extraction. Operational impact categories included (i) behavioral responses; (ii) displacement or habitat exclusion; (iii) acoustic masking and communication effects; (iv) physiological or stress responses; (v) auditory damage or physical injury; (vi) severe outcomes, including strandings or mortality; and (vii) absence of detectable effects.

Data analysis

Analyses focused on quantifying temporal occurrence, thematic distribution, and participation patterns associated with acoustics and anthropogenic underwater noise. Document production was examined through annual counts and proportions relative to total Scientific Committee output. Temporal patterns were assessed by identifying years of occurrence and first appearances of acoustic research, underwater noise topics, sound-source categories, and subcommittee involvement. Comparisons were conducted between documents addressing acoustics broadly and those explicitly referring to underwater noise.

The distribution of documents across IWC Scientific Committee subcommittees and working groups was quantified to evaluate institutional contexts in which topics emerged and developed over time. Frequencies of standardized underwater noise source categories were calculated overall, annually, and across subcommittees to describe patterns of occurrence within the archive. Institutional and national participation were analyzed based on affiliations extracted from each document. The number of documents associated with each institution and country was calculated, and temporal participation was described using the first and last year of occurrence.

Descriptive statistics were applied throughout the analyzes, including counts, proportions, and summary measures used to characterize distributions across documents and categories. Continuous variables are reported as mean ± standard deviation (SD) unless otherwise specified. All analyzes were conducted using R software (R Core Team, 2020), and results were synthesized using descriptive tables and graphical visualizations.

Acoustic-related documents

A total of 7,830 documents produced by the IWC Scientific Committee (SC) between 1951 and 2024 were analyzed. Annual document counts were available for 70 years within this period, with no records for 1955, 1956, 1964, and 1974. After keyword searches, 2,949 documents were screened to assess their eligibility according to the inclusion and exclusion criteria. Following keyword screening and the application of these criteria, 644 documents were retained for analysis, including documents addressing anthropogenic underwater noise as an environmental or management issue without employing acoustic methods directly.

Among the selected documents, 594 were classified as related to acoustics, representing 7.4% of the committee’s total production. Acoustic research occurred in 50 distinct years between 1962 and 2024 (Figure 1). Until 1994, annual counts were low (one to seven documents), followed by a marked increase from the late 1990s onwards, including a peak in 1999 (n = 38). Since then, acoustic documents have occurred continuously (Figure 2A). Across all 70 years with annual records (including years with no acoustic documents), acoustic outputs averaged 8.5 ± 9.5 documents per year, ranging from 0 to 38. When considering only years with at least one acoustic document, annual counts ranged from 1 to 38, with a mean of 11.9 ± 9.2 documents per year. The annual proportion of acoustic documents averaged 5.5 ± 5.8%, ranging from 0% to 33.3%.

Acoustic documents were associated with 33 SC subcommittees and working groups. The largest contributions came from the Small Cetaceans Sub-Committee (SM; n = 106; 18.1%), the Southern Hemisphere Whale Stocks Sub-Committee (SH; n = 102; 17.4%), and the Environmental Concerns Sub-Committee (E; n = 81; 13.8%), which together accounted for 49.3% of all acoustic documents (Figure 2A). The first acoustic document in the dataset (1962) was not associated with a specific committee. The earliest committee-linked acoustic documents appeared in the Sub-Committee on Population Structure (PS) in 1980, followed by the Working Group on Special Permit Research (SP) in 1982, Right Whales (RW) in 1983, and Other (O) in 1985.

The first acoustic-related document identified in the SC archive dates to 1962 and consists of a national progress report from the Netherlands Whale Research Group. Acoustic research appears under the section “Research on Hearing and Sound Production of Cetacea” and focuses on directional hearing experiments conducted on a live harbor porpoise, as well as theoretical considerations linking strandings to potential failures in sonar-based orientation in shallow or muddy coastal environments. No further acoustic-related documents were identified between 1963 and 1969. Acoustic content was next identified in 1970. During that decade, acoustics appeared in distinct contexts: bioacoustic recordings and behavioral correlations (1970), experimental auditory research (1971), acoustic playback for bycatch mitigation (1973), and operational sonar (ASDIC) in relation to catch efficiency and stock assessment (1978).

Underwater noise documents

A total of 180 documents addressing underwater noise were identified in the SC archive (2.16% of total production). The earliest explicit reference to underwater noise as an environmental issue occurred in 1979, and the topic appeared in 38 distinct years between 1979 and 2024. Across the 70 years with available records, annual counts averaged 2.6 ± 3.4 documents (range: 0–12); restricting to years with at least one document, counts ranged from 1 to 12 (mean: 4.7 ± 3.3). The annual proportion of underwater noise documents averaged 1.34 ± 1.58% (range: 0%–5.07%). Occurrence was sporadic through the 1980s and early 1990s, followed by a progressive increase from the late 1990s onward, with peaks in 2004 and 2006 (n = 12) and in 2009 and 2010 (n = 11) (Figure 2B).

Underwater noise documents were associated with 15 SC subcommittees. Among the 33 SC subcommittees represented, 17 did not address underwater noise. The In-depth Assessment subcommittee (IA) and Ecological Modeling subcommittee (EM) contributed 15 and eight documents, respectively, none referring to noise; SP contributed five, and the remaining 15 sub-committees contributed three or fewer documents without noise references. The greatest contributions addressing underwater noise came from E, followed by SM and Whale Watching (WW), which together accounted for 66.9% of all underwater noise documents. The first underwater noise document identified (1979) was not associated with a specific committee. Committee-level engagement began in the early 1980s, first appearing in PS in 1982 and RW in 1983, followed by a broader incorporation across additional committees during the 1990s and subsequent decades (Table 2).

The first two documents identified as addressing underwater noise in 1979 framed the topic as an emerging environmental concern, although still analytically underdeveloped. One of them referred to ship-generated noise as an ecological factor neglected in comparison to the impacts of whaling, noting that maritime traffic could exert ecosystem-level effects despite the absence of specific countermeasures. The other document explicitly employed the term “noise pollution” and described the ocean as increasingly dominated by vessel traffic and sonar use. Other human activities, including military operations, oil drilling, mineral exploration, and seismic testing, were discussed separately as forms of habitat encroachment. Noise was described as a potential source of stress in sperm whales, particularly when associated with prior experiences of being hunted.

Sources of underwater noise

Sound sources were grouped into 10 categories (Table 2). Shipping and sonar were the first anthropogenic noise sources reported (1979), followed by oil and gas activities and seismic sources (1984), marine construction (1987), and explosions (1994). New categories appeared progressively thereafter, including acoustic deterrents and scientific acoustic experiments (1998), windfarm noise (2002), and mining, first recorded in 2021 within the Human Induced Mortality Sub-Committee (HIM).

During the 1980s and early 1990s, most sources were recorded in single documents per year. From the late 1990s onwards, multiple source categories began to be reported within the same year, with increasing annual frequencies particularly for shipping, seismic, and sonar. Seismic sources reached the highest annual frequency, with up to 12 documents in 2006, while shipping reached annual values of up to eight documents in 2004 and 2009. Marine construction sources peaked at five documents in 2009, whereas oil and gas activities reached a maximum of three documents per year across multiple years. Other categories occurred at lower annual frequencies, typically ranging from one to two documents per year (Figure 3).

Across the entire study period, shipping was the most frequently cited source of underwater noise (n = 101 documents), followed by seismic (n = 83) and sonar (n = 41). Intermediate frequencies were observed for marine construction (n = 29) and oil and gas activities (n = 25), whereas offshore wind energy (n = 12), acoustic deterrents (n = 9), and explosions (n = 8) were less frequently reported. Mining and scientific acoustic experiments were the least cited categories, each occurring in three documents. The E subcommittee encompassed the greatest diversity of sound source categories (n = 10), including seismic, shipping, marine construction, oil and gas activities, acoustic deterrents, explosions, mining, scientific acoustic experiments, sonar, and windfarm-related noise. This was followed by the SM, which addressed nine source categories. The remaining subcommittees considered between one and five sound sources (Table 2).

Reported impacts by anthropogenic underwater noise source

The historical record of documents submitted to the IWC Scientific Committee highlights two broad characteristics of anthropogenic underwater noise. Chronic and diffuse sources, particularly navigation and commercial shipping, were described as elevating background acoustic levels over extended temporal periods and across large spatial scales. In contrast, impulsive or high-intensity sources, such as military sonar, seismic air guns, and underwater explosions, were reported as producing acute impacts, including injury and mortality in extreme cases.

Noise associated with vessel traffic was primarily reported in relation to acoustic masking, vocalization changes, behavioral responses, and spatial displacement. Documents describe reductions in acoustic communication range, changes in vocalization rate and structure, and avoidance responses, including changes in direction and swimming speed. Stress responses and behavioral alterations associated with vessel proximity and traffic intensity were also reported, and in some cases references to injury or mortality were described in association with vessel operations.

Seismic surveys were reported in association with a wide variety of responses, including absence of detectable effects, behavioral changes, alterations in diving and respiration patterns, temporary displacement, acoustic masking, stress responses, and temporary auditory damage. Documents also recorded changes in acoustic behavior associated with foraging and detecting seismic signals over long distances. In some cases, strandings were described as occurring temporally close to seismic operations, without conclusive determination of causality.

Sonar, particularly in military contexts, was reported in association with intense behavioral responses, including flight reactions and abrupt changes in diving behavior, as well as acoustic masking and temporary auditory damage (TTS). Documents also recorded stranding events, including mass strandings of beaked whales, and reports of mortality temporally associated with high-intensity sonar exercises. Some records mentioned findings compatible with physiological and tissue injuries, including references to decompression-like sickness and gas embolism.

Activities related to offshore oil and gas exploration and production were reported in association with behavioral alterations, area avoidance, spatial displacement, changes in vocalizations and call rates, alterations in migratory routes, and acoustic masking. Some documents also described physiological responses associated with noise exposure, including short-range auditory effects, as well as changes in habitat use near platforms and associated operations. In certain cases, limited responses or absence of detectable changes was also reported.

Noise associated with marine construction and windfarm installation, including pile driving and structure installation, was reported in association with behavioral disturbance, reduced acoustic detections, vocalization changes, temporary displacement, and potential short-range auditory damage. Documents also described detectable responses across broad spatial scales, as well as reduced acoustic presence during active construction periods followed by return after operations ceased. In some cases, uncertainty was reported regarding whether reduced detections reflected animals leaving the area or cessation of vocalization when acoustic monitoring alone was used.

Underwater explosions were reported in association with acute effects, including physical trauma, auditory damage, immediate flight responses, and mortality. Documents described these sources as high-intensity events capable of producing shock-wave injuries and physiological damage. Records included post-detonation behavioral observations and findings compatible with injuries associated with explosive exposure, as well as reports related to repeated operational use of explosives in some contexts.

Acoustic deterrent devices, including pingers and acoustic harassment devices (AHDs), were primarily reported in association with avoidance responses, spatial repulsion, and the formation of habitat exclusion zones. Some documents also mentioned potential auditory risk during close exposure to higher-power devices, and responses were reported to vary among species and operational contexts.

Deep-sea mining was described as an emerging source of continuous noise. Documents reported potential acoustic masking, behavioral disturbance, and spatial displacement based primarily on prospective assessments and acoustic modeling studies. Modeling results also indicated that operational noise may exceed behavioral disturbance thresholds near sources and alter the acoustic environment across broad spatial scales.

Scientific acoustic experiments were reported in association with behavioral changes and alterations in spatial distribution, including observations of animals occurring at greater distances from acoustic sources. In some cases, mortality events were described as occurring temporally close to experimental operations, without confirmation of a causal relationship.

Across all noise source categories, the most frequently reported impacts were behavioral responses and habitat displacement. Auditory damage and mortality were primarily described in association with short-duration, high-intensity sources such as sonar and explosions. Documents also reported variable outcomes among studies, including cases in which no detectable effects were observed under specific exposure conditions.

Institutional and country participation

A total of 559 distinct institutions were identified among documents simultaneously classified as addressing acoustics and/or underwater noise. Institutional participation was associated with 3.2 ± 8 documents per institution, with 50% appearing in a single document and 75% appearing in three or fewer documents.

The National Oceanic and Atmospheric Administration (NOAA) was the most frequently represented institution, contributing to 146 documents between 1980 and 2024. Curtin University appeared in 47 documents, followed by the University of Newfoundland and the Whale and Dolphin Conservation Society, each represented in 44 documents. Cornell University contributed 42 documents, while entries categorized as “government” accounted for 41 documents. Other recurrent contributors included the Wildlife Conservation Society (32 documents), the University of St Andrews (29), Scripps Institution of Oceanography (25), and the International Fund for Animal Welfare (23). Oregon State University, the Environment Society of Oman, and the Woods Hole Oceanographic Institution each appeared in approximately 20 documents. Several institutions were associated with between 14 and 17 documents, including Fundación Cethus, George Mason University, New England Aquarium, the University of Pretoria, North Slope Borough, Five Ocean Environmental Services LLC, and the University of Exeter. The remaining institutions were represented in fewer documents (Supplementary Table 1).

For documents classified exclusively as related to underwater noise, 214 distinct institutions were identified. Institutional participation was associated with 2.0 ± 3.7 documents per institution, with 50% of institutions appearing only once and 75% appearing in two or fewer documents. NOAA remained the most frequently represented institution (43 documents), followed by Whale and Dolphin Conservation (22 documents) and George Mason University (17 documents). Contributions from other institutions were comparatively limited, with most appearing in fewer than 10 documents (Supplementary Table 1).

Documents addressing acoustics and/or underwater noise within the SC between 1962 and 2024 were contributed by 75 countries (Supplementary Table 2). The mean contribution was 14.7 ± 41.6 documents per country, ranging from 1 to 328 documents over the study period. Approximately 32% of countries contributed only a single document, whereas fewer than 10% contributed more than two documents, and 58.6% contributed three or more documents. The earliest recorded participation corresponded to the Netherlands in 1962, followed by the United States in 1970 and Canada in 1981. The most recent countries were Bulgaria and Panama, in 2024. The United States was the leading contributor with 328 documents, followed by the United Kingdom with 138 documents and Australia with 87 documents (Supplementary Table 2).

Documents classified as addressing underwater noise were contributed by 49 countries. The contribution was 5.8 ± 14.6 documents per country, ranging from 1 to 94 documents over the study period. The United States accounted for 94 documents, followed by the United Kingdom with 48 documents and Australia with 13 documents. All remaining countries contributed nine or fewer documents each. Participation in underwater noise research began with the United States in 1982 and expanded progressively from the mid-1990s onward, with most countries entering this research area after 2000 (Supplementary Table 2).

At the continental scale, North America included seven contributing countries, with 15.6 ± 34.7 documents per country. Europe comprised 22 contributing countries, with 5.09 ± 9.88 documents per country. Participation from Africa began in 1997 and included five countries, with 2.2 ± 1.64 documents per country. Oceania followed in 1998, comprising three contributing countries and 7.33 ± 6.03 documents per country. Asia appeared in 1999, with five contributing countries and 2.8 ± 2.68 documents per country. South America entered in 2004, totaling seven contributing countries with 2.57 ± 2.15 documents per country.

The analysis of documents submitted to the SC reveals the progressive emergence and increasing institutional recognition of acoustics and anthropogenic underwater noise within the scientific and environmental scope of the Commission. By integrating systematic document screening, thematic classification, and scientometric analysis, this study provides the first long-term structured synthesis of how knowledge related to acoustics and underwater noise has been produced, organized, and discussed within the SC. The results demonstrate that acoustics functions as a transversal axis connecting multiple research areas and subcommittees, whereas underwater noise emerges as an increasingly prominent environmental concern associated with impact assessment. The analyzed corpus therefore constitutes a unique institutional record that allows reconstruction of the internal evolution of scientific priorities and discussions concerning acoustic pressures in the marine environment, providing an integrated basis for future analyzes of governance, mitigation, and conservation of the ocean acoustic environment.

Historical development of acoustic and underwater noise research within the SC

Acoustic documents were distributed across five decades (1962–2024), with a marked increase from the late 1990s onwards and a peak in 1999. The emergence of acoustic studies during the early 1960s coincides with the period in which bioacoustics research became technically feasible, following the transfer of recording and monitoring technologies originally developed for naval applications to scientific research and the gradual improvement of sound recording and analysis equipment (Fish and Mowbray, 1970). Early bioacoustics investigations nevertheless remained limited due to technological constraints and labor-intensive analytical procedures (Pavan et al., 2022). The expansion observed from the late 1990s is consistent with advances in digital recording, storage, and analytical technologies that increased accessibility, recording duration, and data-processing capacity (Pavan et al., 2022).

The peak in 1999 is associated with a targeted agenda item within the SM subcommittee addressing bycatch mitigation measures, specifically acoustic devices (International Whaling Commission (IWC), 2000), which contributed to the concentration of contributions in that year, particularly those related to acoustic deterrents such as pingers. This pattern is consistent with the broader scientific context of the 1990s, when bycatch in gillnet fisheries had already been recognized as a major global threat to small cetaceans (Jefferson and Curry, 1994), and experimental evidence began to support the effectiveness of acoustic deterrent devices as mitigation tools (Kraus et al., 1997).

In contrast, underwater noise emerged later and in lower volume, with 180 documents recorded between 1979 and 2024 and peaks in 2004 and 2006, indicating a gradual incorporation of the topic into SC scientific discussions. Early research on underwater sound was primarily driven by military applications, with hydrophones used to detect submarines since World War I and ship noise initially treated as a technical limitation for sonar systems during World War II (Lemon, 2004). Following the Second World War, rapid technological expansion led to a substantial increase in global maritime activity, including intensified commercial shipping and the development of powerful naval acoustic systems during the Cold War, when sonar and large-scale underwater listening networks were deployed for submarine detection (Holler, 2014). During the 1970s, the recognition of long-range acoustic communication in baleen whales (Payne and Webb, 1971), together with the growing understanding of sound as a primary sensory modality for cetaceans, fundamentally transformed scientific perspectives on marine mammal ecology. Consistent with this historical transition, bibliometric analyzes indicate that underwater-noise research began to diversify conceptually during the 1970s and expanded rapidly after the 1990s, reflecting a broader shift from physical acoustics toward ecological and conservation-oriented research (Williams et al., 2015). This correspondence suggests that temporal trends observed within the IWC Scientific Committee mirror broader transformations in the global development of ocean-noise science.

The distribution of documents across subcommittees reveals that acoustics and underwater noise occupy distinct institutional roles within the SC. Acoustic-related documents were distributed across 33 subcommittees, suggesting that acoustics primarily functions as a transversal scientific tool supporting multiple research domains (Laiolo, 2010; Penar et al., 2020; Pavan et al., 2022). In turn, the distribution of underwater-noise documents indicates a process of institutional diffusion accompanied by patterns of concentration within specific subcommittees, rather than a homogeneous presence across the SC. The E, SM, and WW subcommittees collectively concentrate most noise-related documents, indicating that these groups constitute the principal institutional spaces in which the topic is discussed with greater intensity. Rather than representing exclusive domains, these subcommittees configure recurring arenas of deliberation in which underwater noise is addressed as an environmental concern, as an anthropogenic pressure associated with effects on small cetacean species and populations, and as an element related to contexts of human–wildlife interaction.

Participation in acoustics and underwater noise research within the Scientific Committee was geographically and institutionally broad but highly concentrated among a limited number of contributors. Although 559 institutions and 75 countries were represented in the overall record, most institutions contributed only once or a few times, while a small group of recurrent contributors accounted for a substantial share of documents. This concentration was even more pronounced for underwater noise specifically, where half of the institutions appeared in a single document, indicating limited continuity of participation. The prominence of a few institutional hubs, particularly governmental and long-term research organizations, suggests that knowledge production within the SC relies on sustained centers of expertise. At the same time, the progressive entry of new regions reflects an expanding but still uneven global engagement, highlighting opportunities to strengthen continuity and capacity among emerging contributors.

Anthropogenic sound sources and their impacts

The temporal sequence in which sound-source categories appear within SC documents reflects a progressive broadening of the Committee’s noise agenda in response to evolving human activities in the ocean. The earliest references, emerging in 1979, focused on shipping and sonar, followed by seismic surveys and oil and gas activities in 1984, marine construction in 1987, explosions in 1994, acoustic deterrents and experimental sources in 1998, windfarm-related noise in 2002, and most recently deep-sea mining in 2021. Rather than representing isolated additions, this chronological pattern suggests the gradual incorporation of new industrial and technological pressures as they entered marine environments and scientific debate (Simmonds et al., 2014). The progressive appearance of new categories indicates a broadening of the SC noise agenda from traditional maritime and military sources toward increasingly diverse industrial frontiers, reflecting the Committee’s adaptive response to emerging anthropogenic uses of the ocean.

The relative frequency of categories more clearly elucidates how these pressures have been institutionally prioritized within the SC. Shipping, seismic surveys, and sonar dominate the dataset, indicating sustained attention to both chronic acoustic sources and high-intensity energy sources. While shipping represents a persistent pressure associated with increasing ocean background noise (UNCTAD, 2018; Erbe et al., 2019), seismic surveys and sonar correspond to episodic yet high-energy sources that are frequently linked to heightened scientific concern and more intensive regulatory discussions (Gordon et al., 2003; Parsons et al., 2008; Nowacek et al., 2015). The more recent emergence of categories such as offshore windfarm construction, experimental sources, acoustic deterrent devices, and deep-sea mining signals an expansion of the Scientific Committee’s scope toward new ocean-industrial frontiers. Taken together, these patterns indicate not only a diversification of anthropogenic acoustic pressures but also a progressive broadening of the Committee’s institutional agenda, as emerging technologies and new ocean uses become incorporated into scientific assessments and policy-relevant deliberations.

Across noise source categories, behavioral responses and habitat displacement emerged as the most consistently reported impacts, occurring across both chronic and impulsive acoustic sources. This cross-source pattern reflects not only ecological sensitivity to disturbance but also the types of responses most readily detectable within observational and monitoring frameworks commonly used in marine mammal research. Changes in movement, vocal behavior, and space use can be identified across a wide range of study designs and exposure contexts, making them recurrent features of the historical record (Richardson et al., 1995; Erbe et al., 2019; Popper and Hawkins, 2019). The predominance of behavioral and spatial responses therefore indicates a convergence between ecological relevance and methodological detectability, highlighting disturbance as a central dimension through which anthropogenic noise has been assessed within the Scientific Committee.

In contrast, auditory damage and mortality were reported primarily in association with short-duration, high-intensity sources such as military sonar and underwater explosions, suggesting a differentiated impact regime linked to acoustic intensity and exposure characteristics. Underwater explosions produce low-frequency shock waves capable of propagating over long distances, posing mortality risks at close range (<100 m) and causing acoustic trauma, including temporary or permanent hearing impairment, at greater distances, with broader life-cycle disturbances reported further from the source (Ketten, 1995; Southall et al., 2007; Au and Hastings, 2008; Bagočius, 2013). Similarly, military sonar generates intense mid-frequency signals that can elicit strong behavioral reactions and abrupt alterations in diving patterns, which in some cases have been linked to physiological disruption, gas embolism, and decompression-like sickness, particularly in deep-diving species such as beaked whales (Jepson et al., 2003; Fernández et al., 2005; Cox et al., 2005; Parsons et al., 2008). Together, these findings indicate that acute, high-intensity acoustic exposures are disproportionately associated with severe physiological outcomes, distinguishing them from the behavioral disturbances reported for chronic noise sources.

Importantly, the documentary record also includes reports of absent or inconclusive effects, as well as temporal associations without demonstrated causality, particularly in relation to seismic activities and stranding events. Such outcomes may reflect variability in received sound levels, behavioral context, habituation processes, and methodological limitations affecting detectability, rather than the absence of biological effects (Richardson et al., 1995; Carroll et al., 2017). Similarly, mass stranding events temporally associated with naval sonar exercises have been repeatedly documented, although causal mechanisms remain complex and context dependent (Parsons et al., 2008). Together, these patterns highlight the evidential complexity surrounding acoustic impacts, where observed associations do not always permit definitive causal attribution. This distinction between chronic disturbance and acute injury outcomes may provide a useful framework for management considerations, supporting differentiated mitigation approaches according to exposure type and evidential confidence.

Translating scientific evidence on anthropogenic underwater noise into policy and governance

The historical trends identified in this study demonstrate that anthropogenic underwater noise has evolved from a specialized scientific topic into a central conservation issue within the IWC Scientific Committee (SC). The increasing number of documents, the expansion across multiple subcommittees, and the diversification of anthropogenic sound sources reflect the maturation of scientific evidence available to support conservation decision making. Consequently, the patterns identified here extend beyond scientometric trends and illustrate how the accumulation of scientific evidence on anthropogenic underwater noise has progressively informed international marine governance.

Within the IWC, the translation of scientific evidence into conservation policy occurs through complementary institutional roles. The SC is responsible for providing the scientific basis for conservation decision making by identifying priority populations, assessing threats such as shipping noise and seismic surveys, defining monitoring objectives, conducting comprehensive literature reviews, and providing technical advice. The Conservation Committee (CC), in turn, translates these scientific assessments into tangible management and governance outcomes through policy advocacy, implementation, coordination, and the development of international partnerships based on the SC’s technical recommendations. This complementary relationship between the SC and the CC provides the institutional pathway through which scientific evidence is translated into conservation policy and management.

The institutional evolution of anthropogenic underwater noise within the commission reflects this science-policy interface. Building on the Commission’s earlier recognition of anthropogenic underwater noise as a priority topic for investigation under Resolution 1998-6 (International Whaling Commission (IWC), 2018), the IWC adopted Resolution 2018–4 on Underwater Noise by consensus, recommending actions by contracting governments, the SC, the CC, and the IWC Secretariat to improve the understanding, reduction, and mitigation of underwater noise (International Whaling Commission (IWC), 2018). During the same meeting, the Commission established the Intersessional Correspondence Group on Anthropogenic Underwater Noise (ICG-AUN), with the explicit mandate to “consider and act upon, as appropriate, the advice and recommendations from the SC on the impacts of anthropogenic underwater noise” (International Whaling Commission (IWC), 2018). Collectively, these institutional developments demonstrate how scientific evidence generated within the Scientific Committee has been translated into governance mechanisms within the Commission.

The subsequent activities of the ICG-AUN further demonstrate how outputs from the Scientific Committee have contributed to international policy processes. In September 2023, the IWC Secretariat participated in an IMO workshop examining opportunities to reduce underwater noise (International Whaling Commission (IWC), 2026). Findings generated by the SC provided the scientific basis for the IWC’s contribution to the United Nations Secretary-General’s Report on Anthropogenic Underwater Noise, prepared for the Open-ended Informal Consultative Process on Oceans and the Law of the Sea (International Whaling Commission (IWC), 2026). Scientific evidence compiled by the IWC also enabled the Commission to contribute directly to the development of the IMO Revised Guidelines for the Reduction of Underwater Noise from Commercial Shipping, adopted at MEPC80 (July 2023) and issued as Circular MEPC.1/Circ.906 in August 2023 (International Whaling Commission (IWC), 2026). Furthermore, the CC is currently developing guidance materials to support Contracting Governments in implementing these revised IMO guidelines into national law (International Whaling Commission (IWC), 2026). More broadly, the IWC uses the complementary roles of the SC and the CC to conduct scientific assessments and engage with other intergovernmental organizations, including the Convention on Migratory Species (CMS) and the Convention on Biological Diversity (CBD), to support additional work on the dissemination of guidance for seismic exploration and offshore renewable energy (International Whaling Commission (IWC), 2024, 2026).

Finally, the present scientometric review represents an additional step in this science-policy process. Rather than serving solely as a historical synthesis of Scientific Committee activities, the present review is already slated for use as a direct management tool by the IWC. According to the ICG-AUN Workplan (2025–2028), the review will serve as a gap-analysis tool to identify management areas where scientific evidence is currently limited. The findings of the present review will support the Conservation Committee in developing implementation toolkits and non-technical fact sheets to assist policymakers and contracting governments in implementing evidence-based conservation strategies (International Whaling Commission (IWC), 2026). Consequently, beyond documenting the historical evolution of anthropogenic underwater noise within the Scientific Committee, this study provides an evidence base for future governance, policy development, and conservation planning within the IWC. In doing so, it demonstrates how scientific evidence generated within the Scientific Committee can be translated into tangible conservation, management, and policy outcomes.

This study provides the first long-term systematic synthesis of how acoustics and anthropogenic underwater noise have been incorporated into the scientific and institutional agenda of the IWC Scientific Committee across more than seven decades of scientific activity. By combining systematic document screening with scientometric and qualitative analyzes, the study demonstrates that acoustics evolved from a specialized methodological field into a transversal component of marine mammal research, while underwater noise progressively emerged as a policy-relevant environmental issue across multiple subcommittees and governance contexts.

The historical expansion and diversification of anthropogenic sound sources documented within the Scientific Committee reflect broader transformations in ocean industrialization, marine governance, and environmental awareness. At the same time, the concentration of contributions among a limited number of institutions and countries highlights persistent asymmetries in scientific participation and knowledge of production within international marine conservation frameworks.

Together, these findings establish a historical and institutional baseline for understanding the evolution of ocean-noise research within the IWC. They also demonstrate how the accumulation of scientific evidence within the Scientific Committee has informed governance mechanisms and international policy processes related to anthropogenic underwater noise. As such, this review provides an evidence base for future investigations integrating governance, mitigation effectiveness, scientific collaboration, and conservation policy while also supporting evidence-informed conservation decision making related to the marine acoustic environment.