Reducing Noise in National Parks

(Inside Science) -- The Natural Sounds and Night Skies Division at the U.S. National Park Service provides scientific support to all the national park units. Its researchers help park administrators understand the current state of their resource conditions and what the effects of pollution are on visitor experience and wildlife, and give them suggestions for how they might reduce pollution and mitigate its consequences.

Kurt Fristrup, Ph.D., of Natural Sounds and Night Skies, said, “Noise and light pollution are interesting because most of the forms of pollution involve matter. The pollution we work on involves energy and has the interesting property that as soon as you do something about the source, the environmental conditions improve immediately.”

Historically the Park Service became interested in noise pollution when the Grand Canyon National Park was enlarged by Congress in 1975. The legislation spoke of natural quiet as a resource and a value to be protected in the park.

Noise interferes with hearing, just as smog interferes with scenic quality. For visitors, the consequences are a sort of degradation of the quality they experience. For wildlife, the consequences are more severe. Subtle sounds of nature often play critical roles in predator-prey interactions, and other literally life-and-death matters.

There is a real potential for noise impacts. In ultrasounds, for the frequencies above our nominal range of hearing, atmospheric absorption is really strong, but it fades out very quickly with distance.

Infrasound, on the other hand, is a very different matter. Infrasound carries so far across the landscape that infrasound from breaking waves on both coasts of the United States can actually be measured in the Rockies.

The good news is there are very few organisms that are more sensitive to low frequency sounds than we are. The Natural Sounds and Night Skies Division has been systematically monitoring sound levels throughout the National Parks System, from about 600 sites in over 80 park units. Even though that sounds like a lot of data, the department has fairly sparse coverage of all the national parks; there are more than 400 park units. So scientists have begun creating a model that predicts what sound conditions are throughout the National Parks System from these 600 sites.

The Natural Sounds and Night Skies Division recorded about 1.5 million hours across all these different sites. In the time recorded, 25 percent, or about 15 minutes in each hour, has audible noise. This is true even in remote wilderness areas in national park areas. The primary factor, as one might suspect, is aircraft noise.

You can make a difference really quickly by making sure that your own transportation systems are as quiet as today’s technology can reasonably allow.

Scientists are investigating the use of quiet pavements on many of our roads, and Congress requires researchers to work with the Federal Aviation Administration, which controls air space, to develop airport management plans for every park where commercial air travel takes place. Also, researchers are working to shift the traffic into places where there will be fewer noise sensitive receptors on the ground. Additionally, signs are posted in places to advise visitors to try and be quiet. Scientists found that simply asking was equivalent to cutting the number of visitors in the park by half.

Modifying environments by improving light and sound conditions offer one of our best opportunities for making an improvement to environmental quality, to help both the quality of visitor experience and the integrity of the ecosystems, and to improve and be buffered against some of these other environmental changes.