Synthesis of Studies on the Effects of Noise

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1978-2021, with 2021 update

Project Summary

The Natural Resource Stewardship and Science Directorate (NRSS) develops, utilizes, and distributes the tools of natural and social science to help the National Park Service (NPS) fulfill its core mission: the protection of park resources and values. For scientific topics experiencing rapid growth in knowledge, producing a balanced summary of this knowledge is challenging, especially because the most recent articles may contain crucial, relevant information for management of resources and visitor experience. This project addresses the challenge of realizing balanced coverage through a stringent application of a systematic, comprehensive queries of the scientific literature.

Noise arising from expansion of human population and infrastructure, transportation networks, and resource extraction alter conditions in public lands and protected areas, including national parks (Figure 1)¹. A comprehensive query that captures the relevant literature on noise impacts to wildlife and park visitors was developed by experts who conducted original research in this area and published an authoritative synthesis of the literature². That published synthesis offered an important, peer-reviewed summary of the state of knowledge at the time of submission. However, its relevance diminishes with time when the literature expands and evolves rapidly. To offer relevant updates, this resource report represents a summary of the results from our systematic annual query of the literature, providing park managers with an accessible perspective of the size and scope of the relevant scientific knowledge regarding the effects of noise on wildlife and park visitors.

We emphasize the distinction between our approach and the results from an ad hoc query using Google Scholar or a related tool. Our query was developed and tested - by experts in the field - to ensure that the results encompassed all the relevant literature. This query was reviewed and improved in an iterative process. Though no query can guaranty it will capture every relevant paper, our current query delivers results that are far more comprehensive than our initial searches, even though those initial searches were performed by experts in the field. In the context of offering a comprehensive, balanced assessment of the literature of noise effects on humans and wildlife, we are confident that our present query is the best tool to identify the pertinent papers.

This resource brief represents our continued attempt to concisely render knowledge of noise effects on wildlife and people in an accessible format. The focus here is on the size of the literature, the kinds of noise sources that were studied, and the breadth of effects that have been documented. We believe the value of this brief to NPS managers is to raise awareness of the extent of scientific support for park planning and management, and identification of distinct subsets of this literature that may be of special relevance for specific locations or management actions. The authors will assist parks and regions with more detailed and specific analyses of this literature upon request.

Figure 1. Within national parks, aircraft (a) and vehicle noise (b) are most frequently heard whereas train (c) and watercraft (d) are the loudest noise sources. Analysis is based on acoustic recordings collected and analyzed at 247 sites in 64 national parks across the United States³

Finding Relevant Studies

We conducted a peer-reviewed literature search using Thompson's ISI Web of Science (WOS). The search included papers published after 1977 to ensure all relevant literature was captured. The search was optimized to capture a known list of relevant studies. Ninety percent of the studies were captured using our search criteria. We feel that enlarging the query beyond its present scope is likely to add very few relevant papers, at the expense of adding many more irrelevant papers.

The final search for papers published between 1978-2018 resulted in 2,474 studies. We conducted additional searches following the same protocol in subsequent years up to and including 2021. All papers were reviewed by a subject matter expert such that only studies focused on documenting the effects of anthropogenic noise were included in the final data set (N = 1888 relevant studies from 1978 to 2021). Papers that were not relevant included that those that just summarized noise levels without documenting a response and studies that occurred inside hospitals and vehicles (indoor learning spaces were included, due to their relevance for park interpretation). For the papers deemed relevant, the subject matter expert labeled each paper with a noise source category (e.g. transportation) and effect category (e.g. human, wildlife). Additionally, studies were automatically labeled using key words that appeared in the title of the publication (e.g. sleep, annoyance, birds).

Number of Studies 1978-2021

Over the past few decades there has been a growth in studies documenting the effects of noise on humans and wildlife (Figure 2). Literature on humans remained relatively constant with about 10 publications per year until about 2004 when number of publications in a year nearly doubled. For wildlife, studies did not really appear until early 2000s and saw a large increase in yearly publications after 2010. An increase in review papers on both human and wildlife response occurred in 2010, with highest number of publications in 2021.

Figure 2. The number of peer-reviewed studies published each year (1978-2021) documenting the effects of noise based on our WOS search criteria and manual verification. Note: this graphic excludes studies using laboratory animals. For an alternative way to read this data, see the table at the bottom of this page.

Source of Anthropogenic Noise 1978-2021

All relevant papers were labeled by a subject matter expert with a single category of noise source: noise from built environment (all sources together), recreation, transportation, resource extraction (which included industrial sources), or military. Most of the human studies are focused on transportation noise, while the majority of wildlife studies are focused on noise from urban or built environment. The “other” category reflects several studies on noise impacts from unmanned aerial vehicles (UAVs) (i.e., drones), with unspecified origin (i.e. military, recreation). There was 1 study on UAVs in 2020, and several more in 2021. In 2021, we also located one study on the impacts of anthropogenic noise on plants; previously, this literature has been sparse but may require attention in future years with growth in understanding of noise impacts to plants.

Figure 3. Proportion of studies within different noise source categories. Human studies N = 1077 ; Wildlife studies N = 699. These graphics exclude studies using laboratory animals. Data for figure 3 is included in the alternative text below.

Keyword Trends from 1978 to 2021

From 1978-2021, there were 1077 studies on humans (74 of which were reviews), and 699 studies on wildlife (39 of which were reviews).

In the 1077 studies on human response to noise, there were:

• 415 on traffic
• 201 on aircraft noise
• 280 on annoyance
• 71 on wind farm noise
• 144 on sleep
• 48 on industrial noise
• 35 on hypertension
• 19 on speech
• 9 studies in parks or protected areas

In the 699 studies on wildlife response to noise, there were:

• 90 on traffic noise
• 34 on underwater sonar
• 17 on chronic noise
• 10 on aircraft noise
• 9 studies in parks or protected areas

A word cloud of most used words in abstracts on wildlife response to noise studies, 1978-2021 (699 papers). The largest words correspond to the most common words: species, acoustic levels, and survey.

Trends in topics 1978-2021

To examine different topics discussed in the literature, we generated word clouds for wildlife and human studies from the titles and abstracts for all publications (1978-2021).

The animated GIF to the right shows word clouds of topic trends for wildlife publications from 1978-1989, 1990-1999, 2000-2009, 2010-2019, and 2020-2021. Early wildlife publications focused on dolphins and birds, while later studies included more diverse taxa (fish) and noise sources (e.g. urban, sonar, road).

A word cloud of most used words in abstracts on human response to noise studies, 1978-2021 (1077 papers). The largest words correspond to the most common words: traffic, exposure, annoyance.

The animated GIF to the left shows word clouds of topic trends for human publications from 1978-1989, 1990-1999, 2000-2009, 2010-2019, and 2020-2021. Early studies focused on annoyance from aircraft, and later studies included sleep and health effects of multiple noise sources (wind energy, traffic).

2021 Update

The search for publications in 2021 produced 165 papers deemed relevant by a subject matter expert. There were 85 new studies on humans (12 of which were reviews), and 79 new studies on wildlife (8 of which were reviews).

In the 85 studies on human response to noise, there were:

• 27 on traffic
• 14 on aircraft noise
• 24 on annoyance
• 4 on wind farm noise
• 3 on sleep
• 1 on industrial noise
• 1 on hypertension
• 0 on speech
• 0 studies in parks or protected areas

In the 79 studies on wildlife response to noise, there were:

• 7 on traffic noise
• 2 on underwater sonar
• 2 on chronic noise
• 1 on aircraft noise
• 2 studies in parks or protected areas

Figure 4. The number of peer-reviewed studies published each year (2000-2021) documenting the effects of noise based on our WOS search criteria and manual verification. Note: this graphic excludes studies using laboratory animals.

Suggested Reading

Compared with studies on impacts to wildlife and humans, the literature has paid minimal attention to the effects of anthropogenic noise on plants, even though their lack of mobility may make plants particularly susceptible to chronic impacts. Solé et al. (2021) investigated the impacts of anthropogenic noise on an aquatic plant, seagrass (Posidonia oceanica), finding alterations to nutritional processes and changes to the ability to sense gravity and sound vibrations. Because seagrass meadows are a widespread coastal ecosystem and provide many essential ecosystem services, these findings may have broad conservation implications.In a study relevant to parks, people, and birds, Levenhagen et al. (2021) tested experimental quieting as a strategy to improve visitor experience and wildlife habitat quality at Grand Teton National Park. They found that visitors appreciated noise mitigation strategies – which produced better natural soundscape experiences – even if these strategies limited their personal access. Visitors perceived greater bird diversity when noise levels were lower due to mitigation signage. The abundance and composition of bird species, however, did not actually vary according to background noise levels.Gomes et al. (2021) reviewed animal coping mechanisms for dealing with natural noise (like that from wind or snapping shrimp). This effort builds a more quantitative grasp on how natural noise characteristics have shaped animal communities. A deeper understanding of the mechanisms that shape how animals navigate natural noise may provide insights into how they will respond to increasing anthropogenic noise.

• Gomes, D. G., Francis, C. D., & Barber, J. R. (2021). Using the past to understand the present: coping with natural and anthropogenic noise. BioScience, 71(3), 223-234.
• Levenhagen, M. J., McClure, C. J., & Barber, J. R. (2021). Does experimentally quieting traffic noise benefit people and birds?. Ecology and Society. Open Access.
• Solé, M., Lenoir, M., Durfort, M., Fortuño, J. M., Van der Schaar, M., De Vreese, S., & André, M. (2021). Seagrass Posidonia is impaired by human-generated noise. Communications Biology, 4(1), 1-11. Open Access.

Where to Find More Information

A searchable spreadsheet of all the relevant studies is available upon request (see contact information below) or on our website. The spreadsheet will be updated annually, and an annual briefing document will be prepared and appended to this summary. The results will be shared with the NPS community and archived on our website. In most cases, NSNSD staff has access to the full text of the publications and can share a link, email a pdf, or assist in finding the reference.

Project Contacts

Cathleen Balantic, PhD; Sharolyn Anderson, PhD. Natural Resource Stewardship and Science Directorate, Natural Sounds and Night Skies Division. Email: [e-mail]

References

¹Buxton et al. Noise pollution is pervasive in US protected areas. Science 356.6337 (2017): 531-533.

²Shannon et al. A synthesis of two decades of research documenting the effects ofnoise on wildlife. Biological Reviews 91(2016): 982-1005.

³Buxton et al. Anthropogenic noise in US national parks-sources and spatial extent. Frontiers in Ecology and the Environment 17.10 (2019): 559-564.

Alternative text for Figure 1:

(clockwise from top left) Photographs showing different noise sources heard in National Parks. a) helicopter and a herd of bison, b) bus and caribou crossing road, c) train next to a river, d) tour vessel and bears on a nearby beach.

Alternative text for Figures 2 and 4:

The bar graph displays the number of peer-reviewed studies published each year from 1978 to 2021. Five bars are displayed for each year: studies on human response, review papers on human response, review papers on wildlife response and papers on wildlife response. The graph reads:

• 1978: 9 human response studies;
• 1979: 9 human response studies;
• 1980: 8 human response studies;
• 1981: 8 human response studies;
• 1982: 5 human response studies;
• 1983: 12 human response studies; 1 wildlife response study;
• 1984: 4 human response studies;
• 1985: 5 human response studies;
• 1986: 2 human response studies;
• 1987: 7 human response studies;
• 1988: 7 human response studies;
• 1989: 4 human response studies;
• 1990: 5 human response studies; 1 wildlife response study;
• 1991: 8 human response studies; 1 review-human study;
• 1992: 2 human response studies;
• 1993: 6 human response studies; 1 wildlife response study;
• 1994: 10 human response studies;
• 1995: 6 human response studies; 1 wildlife response study;
• 1996: 15 human response studies; 2 wildlife response studies;
• 1997: 13 human response studies; 1 review-human study;
• 1998: 8 human response studies; 1 wildlife response study;
• 1999: 14 human response studies; 2 wildlife response studies;
• 2000: 11 human response studies;
• 2001: 10 human response studies; 1 review-human study;
• 2002: 11 human response studies; 1 review-human study; 3 wildlife response studies;
• 2003: 13 human response studies; 1 review-wildlife study; 7 wildlife response studies;
• 2004: 21 human response studies; 7 wildlife studies;
• 2005: 17 human response studies; 5 wildlife studies;
• 2006: 18 human response studies; 2 review-wildlife; 11 wildlife studies;
• 2007: 21 human response studies; 3 review-human studies; 13 wildlife studies;
• 2008: 23 human response studies; 1 review-wildlife studies; 6 wildlife studies;
• 2009: 34 human response studies; 21 wildlife studies;
• 2010: 39 human response studies; 1 review-wildlife studies; 14 wildlife studies;
• 2011: 35 human response studies; 11 review-human studies; 2 review-wildlife studies ; 34 wildlife studies;
• 2012: 36 human response studies; 3 review-human studies; 57 wildlife studies;
• 2013: 45 human response studies; 1 review-human studies; 42 wildlife studies;
• 2014: 43 human response studies; 2 review-human studies; 1 review-wildlife studies; 37 wildlife studies;
• 2015: 55 human response studies; 3 review-human studies; 1 review-wildlife studies; 43 wildlife studies;
• 2016: 74 human response studies; 6 review-human studies; 67 wildlife studies;
• 2017: 59 human response studies; 5 review-human studies; 4 review-wildlife studies; 57 wildlife studies;
• 2018: 59 human response studies; 13 review-human studies; 2 review-wildlife studies; 56 wildlife studies;
• 2019: 78 human response studies; 5 review-human studies; 5 review-wildlife studies; 54 wildlife studies
• 2020: 73 human response studies; 12 review-human studies; 5 review-wildlife studes; 55 response studies
• 2021: 85 human response studies; 12 review-human studies; 8 review-wildlife studies; 79 response studies

Alternative Text for Figure 3:

The pie charts display proportions of anthropogenic noise sources for peer reviewed studies on noise impacts to humans and wildlife from 1978 to 2021. Human studies N = 1077; Wildlife studies N = 699. For human studies, there were 255 studies on noise from generic/built sources, 1 on military noise, 2 on recreation noise, 137 on resource extraction noise, and 677 on transportation noise. For wildlife studies, there were 333 studies on noise from generic/built sources, 32 on military noise, 6 on recreation noise, 145 on resource extraction noise, and 182 on transportation noise.

Last updated: April 13, 2022