A synthesis of health benefits of natural sounds and their distribution in national parks.

Author: Emma Crumpton
About the Author: Emma Crumpton is a fourth year student at Northwestern University studying music cognition with interests in ecology and sexuality studies. She is passionate about music and art therapies education and research. While finishing up her degree at Northwestern, she enjoys hiking, gardening, indoor plant collecting, reading, and painting.

Soundscapes Without Noise – An Elusive Health Benefit
The true sounds of nature can positively influence health outcomes, but when those sounds are diluted with human-generated noise, the benefits are decreased, according to a recent study.

The study, "A synthesis of health benefits of natural sounds and their distribution in national parks," by R.T. Buxton, A. L. Pearson, C. Allou, K. Fristrup and G. Wittemyer, focused on nature’s sounds and soundscapes, their possible health benefits, and their distribution across U.S. national parks.
 
A soundscape is the collection of sounds perceived in an environment. There are biological sounds like the birds chirping, geophysical sounds like rain falling, and anthropogenic sounds like human voices and road traffic – these last often classified as “noise,” the unwanted sound in natural environments.

Published in March of 2021 the article offers a systematic study of previous literature to look for evidence of benefits of natural soundscapes and to determine to what degree, if any, soundscapes influence health outcomes. It also looks at the distribution of restorative sound environments.

The Buxton team found 36 useful studies, 18 of which they used for a meta-analysis – an examination of data from multiple studies to determine overall trends, of the results. 
 
The results from the literature review showed a 184% overall improvement of health and positive affect in groups exposed to natural sounds, relative to comparison groups. Natural sounds on their own, without other sensory stimuli, can have positive health benefits, such as decreased pain, lowered stress, improved mood, and enhanced cognitive performance.

Water noises were most linked with improvement in health and positive affect, in those exposed to natural sounds, and bird calls were the biggest link to decreased stress and annoyance.

The study then looked at the NSNSD Acoustic Dataset, a data set created by the National Park Service Natural Sounds and Night Skies Division, which has been monitoring acoustic environments since 2000, listening to and observing spectrograms of recordings at 221 sites in 68 parks. These data were used to quantify the distribution of natural sounds and noise across U.S. national parks, considering location and visitation numbers.\
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Of the 221 acoustic monitoring sites analyzed, 75.1% had high audibility of biological sounds and 40.7% had high audibility of geophysical sounds. Bird sounds were audible 42.1% of the time among sites and water-related sounds were audible 22.8% of the time among sites.

Overall, only 11.3% of sites had low audibility of anthropogenic sound and high audibility of biological or geophysical sounds, and 22.6% of sites had moderate audibility of noise and high audibility of biological or geophysical sounds. Such sites with restorative soundscapes may represent important acoustic environments for human health. They also may indicate that restoring soundscapes and eliminating noise could help bolster the potential benefits of these and other sound environments. Yet, accessibility is a factor, as only three sites with high audibility of biological or geophysical sounds and low anthropogenic sound audibility were within 100 km of urban areas, these included parks in Alaska, Hawaii, and the Pacific Northwest.   
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Because noise is an increasing problem in natural spaces, where it can disrupt the everyday functioning of environments and cause health-related problems in people, especially those living in high-noise areas like large cities, these results can inform planning to manage, conserve, and implement activities with natural
soundscapes to enhance human health, like guided soundwalks on nature trails.

Natural soundscapes can be thought of as resources to be protected and enhanced for ecological and human health benefits, such as preserving connections with nature, bolstering biodiversity conservation, and improving
public health.

Citation: "A synthesis of health benefits of natural sounds and their distribution in
national parks." Buxton, R. T., A. L. Pearson, C. Allou, K. Fristrup and G. Wittemyer
https://www.pnas.org/content/pnas/118/14/e2013097118.full.pdf

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