Sources of Human-caused Sounds in National Parks
Since parks were created in part for enjoyment by people, some human-caused sound is present in many park soundscapes. Roads, hikers, vehicles, and maintenance activities are some examples of human-caused sound that may occur in National Park.
Visitors who enjoy national parks using certain modes of access create sound characteristics that impact the experience of other visitors. When visitors view the park via an air or bus tour, an auto, a snowmobile or snowcoach, personal water craft, or motorcycle, intrusive sounds are created for people who have an expectation of quiet, solitude, or appreciation of natural sounds. Often, people who use these modes of access are not even aware of the impact on other people.
Individual sounds do not have to be loud, frequent, or otherwise dominant to have an impact. The total impact to park soundscapes and other resources is often due to the “cumulative effect” of all the sources of sound in a park. It is the combination of sound sources, the acoustic characteristics of each sound (frequency, amplitude, etc), and the physical character of the landscape that determine the impact. The key issue is determining the levels and types of sound that are appropriate or acceptable for different management areas within a park. Click on the pictures to hear some of the human-caused sounds affecting National Parks.
Sounds Sources
Use your pointer to roll over each picture below and learn about the sound source.
Cars, Buses, and Other Vehicles Park Operations Airports and Development |
Airplanes and Helicopters
Watercraft Military Overflights Energy Development |
Solutions
Vehicles
At Zion National Park where visitation doubled between 1982 and 1997 to more than 2.6 million visitors per year, park managers said they had little choice but to ban cars during the park's busiest times and create a mandatory shuttle system. Before the shuttle system began operation, as many as 5,000 cars a day were lining up on holiday weekends to follow the road into the canyon which contained only about 450 parking spaces. According to park staff, the public response to the change, while initially very controversial, has become overwhelmingly positive. Visitors frequently comment that the park is much more serene and peaceful without the multitude of cars.
The Zion shuttle system carried 2.4 million riders last year resulting in a noticeable reduction in vehicular sound levels. The peace and quiet not only had a positive impact on visitors, the effects were also seen in wildlife health and behavior. Over the years, several wildlife species had moved further and further from the main roads to avoid the sound of buses, cars, and other vehicles. Now it’s peaceful enough in the valley that visitors have reported seeing mountain lions from the shuttle buses.
PWC
PWC industry officials emphasize that technological innovations such as baffles, insulation and resonator-equipped mufflers have significantly reduced PWC sound and that newer models are two to eight times quieter than older ones.
Currently only 87 national park units allow motorized boating. The National Park Service has adopted a rule that permanently prohibits PWC use in 66 of those units. Five other park units—Cape Cod National Seashore, Cumberland Island National Seashore, Delaware Water Gap National Recreation Area, Indiana Dunes National Lakeshore, and Whiskeytown National Recreation Area adopted permanent closures for PWCs in 2002.
Park Operations
Denali National Park serves as an example of how parks can minimize sound from park operations. Denali is located in the heart of the Alaska wilderness. It contains some of the most remote places in the National Park system. But not long ago, for Park employees and visitors at Wonder Lake Ranger Station, nature was less than peaceful. A noisy 30-kilowatt diesel generator that powered the station and its buildings ran 24 hours a day. As part of its planning process, the park staff set out to mitigate sound caused by the generator. The Park Service installed a bank of batteries that limited the generator run-time to only 6 to 8 hours every fourth or fifth day to recharge the batteries. As a result, the impact from the generator was greatly reduced and the soundscape was enhanced.