Soundscape ​conservation by the U.S. National Park Service

by Sarah Dumyahn, FNR Graduate Research Assistant

Purdue University’s Human-Environment Modeling and Analysis (HEMA) lab, under the direction of Dr. Bryan Pijanowski, is conducting research on soundscapes found in Tippecanoe County, Indiana. The HEMA lab has made recordings of soundscapes on different Purdue properties that include forests, wetlands, agricultural, and developed lands. Results of this research will begin to identify how Midwestern soundscapes change with land use and how they vary over time. Understanding how soundscapes are affected by land use may also help guide conservation efforts. My research in the lab is focused on soundscape conservation being implemented by the U.S. National Park Service (NPS).

Soundscapes graphic showing noise and natural sounds.
Soundscapes are comprised of all of the sounds within a given area. Many human-generated sounds of motorized travel, yard equipment, and industry are considered noise. In national parks the goal is to identify the appropriate levels of noise so that natural, historical and cultural sounds can be enjoyed. Figure by Sarah Dumyahn.

The NPS protects 392 management units, including national parks, monuments, battlefields, historic sites, recreation areas, lakeshores, and seashores. Within these parks are natural, cultural, and historic resources that are part of America’s heritage. When visiting a national park, such as Yellowstone, most visitors go to see wildlife and view amazing geologic features. But did you realize that contributing to the overall experience at national parks are the sounds that are present? A study conducted by the NPS found that experiencing natural sounds is a major reason why people go to national parks. Some sounds one might expect to hear at Yellowstone include geysers shooting water into the air, elk bugling, wolves howling, rivers rushing, and many different birds singing. A growing body of research indicates that the sounds heard during park visits influence the overall experience.

The NPS has determined that the acoustic environment, like wildlife, water, and scenic views, is a resource worthy of protection. All of the sounds present within an area are considered its soundscape. Many types of sounds can comprise a park soundscape, and they change with time and location within the park. A soundscape can be comprised of natural sounds from wildlife, wind, water, and other geophysical sounds. It can also have historic or cultural sounds, such as cannons or rifles and Native American music. Park soundscapes have other human generated sounds, including visitors talking, children laughing, vehicles on park roads, trains, off-road vehicles (ORVs), boat engines, aircraft flying overhead, and park-operation sounds (i.e., chainsaws, lawnmowers, building construction or repair, and road plowing). How pleasing and appropriate certain sounds are to an individual will vary based on factors such as visitor expectations and the duration and volume of the sounds.

Helicopter flying over Haleakala National Park, Hawaii. 
Aircraft noise is one of the first noise sources to be regulated in parks. This picture shows an air tour helicopter flying over Haleakala National Park, Hawaii. Photo by the National Park Service.

Sounds that are disturbing or annoying are considered noise. The NPS is working to determine what constitutes noise in different parks and how much noise is appropriate to ensure a healthy soundscape that reflects the different parks’ values. Legislation and park policies have been developed mandating that the NPS address this issue. Beginning with its Organic Act of 1916, the NPS has been directed to preserve the resources and ensure the enjoyment of visitors for both this and future generations. This means that the impact of noise sources on park resources and visitors should be determined. Aircraft noise is one of the first noise sources to be addressed by the NPS. In 1987 the National Parks Overflight Act was passed directing the NPS to determine the effects of aircraft on the National Parks System. The Act also required the Grand Canyon to develop an aircraft overflight management plan. Research conducted by the NPS determined that low-flying aircraft had the greatest negative impact on visitor experience and park resources. The majority of these lowfliers are tour operations, also known as flight seeing aircraft. The findings culminated in the National Park Air Tour Management Act of 2000, a law that requires parks with air tours operating over, or just outside the park boundary, to develop a management plan.

The NPS Natural Sounds Program was established in 2000 to help parks develop air-tour management plans. The NPS works collaboratively with the air-tour operators, the Federal Aviation Administration, Native American tribes, and environmental organizations to develop these plans. Soundscape monitoring is one of the first steps in developing alternatives, but it is also used to inform wildlife management, transportation planning, and recreation studies. Monitoring the soundscapes requires deploying automated acoustic recorders. Some recording devices can monitor sounds continuously for extended periods. Audio recordings are analyzed by the Natural Sounds Program or park managers to determine acoustic baseline conditions. Some acoustic characterizations identify different types of sounds that are present, the percentage of time that motorized vehicles are audible, and the volume of motorized sounds. These automated acoustic recorders permanently capture the soundscape conditions that currently exist, creating a database of our acoustic heritage that can be analyzed in other ways in the future.

Spectrogram tool used to analyze sounds.
A spectrogram is one tool that can be used to analyze the sounds in an area. It represents the recorded sounds of a location showing the sound frequency and the time. This spectrogram is from a recording taken at the Purdue University Wildlife Area on April 6, 2008. The top portion contains evening hours showing amphibian vocalizations. The bottom is daytime showing geese and other bird species vocalizations. Photo by Luis Villanueva-Rivera.

For the first phase of my research, I conducted in-depth phone interviews with NPS resource managers at different parks. The first objective was to determine if park managers thought the National Park Air Tour Management Act was mitigating air tour impacts. Parks experience different types of aircraft overflights. High-elevation commercial flights occur over most parks. Some parks were under flight paths for major international airports. Other flight types include: military, air tours, emergency services, park operations, general aviation, and other government agencies. Out of all types, air tours were considered by the managers to have the greatest negative impact on park visitors and resources. Parks with air tours that operated over the park were questioned about developing an air tour management plan. While many parks expressed interest in having an air-tour management plan, none have been completed for any of the parks. The planning process has proven to be difficult. Just over 100 parks have air tours, so the NPS has their work cut out for them.

A secondary objective of the phone interview process was to identify other noise-related issues in parks. Park managers reported many different noise sources that diminish the value of park experiences. Some noises are very park-specific, such as logging or mining operations outside of park boundaries. Yet, most park managers indicated that the noise source of greatest concern was aircraft. The second-ranked noise source of greatest concern was vehicular traffic on park roads. Some parks are actively working to mitigate soundscape impacts. A few are monitoring and conducting research to develop soundscape management plans. These plans will identify desired future soundscape conditions at different locations in the parks. Other parks no longer allowed personal vehicles in certain parts of the park. Instead, visitors take buses to view the unique landscapes. The buses used in one park are electric and extremely quiet. The resource manager reported that the noise from cars used to permeate to the remote and undeveloped backcountry, but that now it is much quieter.

This initial research spurred my current efforts. I am studying the reasons that some parks are implementing soundscape conservation efforts more readily than others. Recently, the Natural Sounds Program distributed a survey to every park unit. The survey asked managers to identify important components of their parks’ soundscapes and measures they are taking to minimize noise impacts. I am analyzing the results and will be contacting some of the parks for follow-up interviews. This research will identify ways to improve soundscape conservation efforts in our national parks.

Park soundscapes are unique resources that contain natural, cultural, and historical sounds. The ability to hear these types of soundscapes is diminishing as development and transportation systems expand. The national parks should protect the opportunities to experience these sounds.

Here's a chance to decide for yourself.

Yellowstone and Grand Canyon landscapes. 

What is your initial reaction to viewing these Yellowstone and Grand Canyon Landscapes?

. . . Now imagine the sounds of flowing water, wind and birds . . .

Does your reaction change if you imagine the natural sounds of these landscapes mixed with the sounds of cars on nearby roads and aircraft engines overhead?

If you are interested in learning more about national park soundscapes, you can go to: For more ground-breaking research articles see FNR Compass 2010.​​

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