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16 CHAPTER SEVEN EFFECTS OF AVIATION NOISE ON PARKS, OPEN SPACE, AND WILDERNESS AREAS In considering the effects of aviation noise on parks in relation (response) data previously collected in the national parks to both animals and humans, there have been new and interest- (Rapoza et al. 2005). The accumulated data consist of almost ing issues not previously considered, particularly concerning 2,500 visitor interviews and simultaneous acoustical measure- restoring and/or maintaining natural quiet in U.S. national ments collected at four different national parks between 1992 parks and Native American tribal lands. Given the often and 1999, including two major FAA dose-response measure- extremely low ambient noise of the parks, aviation noise from ment programs in 1997 (short-hike) and 1998 (overlook). high-altitude aircraft passby or lower-altitude tour operations can be heard for miles. Trying to define the natural soundscape The dose-response data obtained from these studies can be can often be as challenging as defining the noise intrusion and used to determine the relationships between aircraft noise and potential effects. visitor response for purposes of assessing aircraft noise in the national parks. Important results from that 2005 report included the finding that the vast majority of visitors' (92% to NATIONAL PARKS AND 94%) rate annoyance is equal to or higher than interference NATIVE AMERICAN TRIBAL LANDS with enjoyment. Visitors appear to be less sensitive to high- altitude jet overflight noise as compared with noise from tour The study of aviation noise effects on national parks and aircraft. However, the data do not show this with statistical Native American tribal lands began in 1985. Because this is a certainty and no definitive conclusions can be drawn. Visitor completely new research area, a brief history of its develop- response to tour overflight noise differs between overlooks ment and oversight responsibilities is warranted. With the and short hikes. In addition, it appears that a respondent's passage of the National Parks Overflight Act of 1987, the FAA familiarity with the site can influence visitor response to air- and the National Park Service were tasked to join forces and craft noise; that is, repeat visitors generally are more annoyed. begin the process of restoring natural quiet to the nation's parks. In 2000, the National Parks Air Tour Management Act Some of the most provocative new research is by Horon- required commercial tour operators to develop air tour man- jeff (2005) who provides a good summary background of the agement plans (ATMP) and obtain FAA approval to conduct efforts to define methods to quantify the natural soundscape of operations over parks or tribal lands. Any ATMP for a national the wilderness park environment. The author defines the park may prohibit commercial air tour operations, and may es- soundscape in terms of duration of quiet time and time a visitor tablish conditions or restrictions of operations, including noise has to wait until he or she experiences quiet times of certain restrictions, visual restrictions, or other impacts. The National durations. In terms of defining periods of natural quiet for Parks Air Tour Management Act does not provide specific purposes of analyzing transportation projects near parks, the noise limits to be considered as part of the ATMP. Addition- author concludes that the use of computer models is the only ally, the National Park Service's "Soundscape Preservation efficient means by which noise effects may be evaluated over and Noise Management" Director's Order #47 that expired in large areas. 2000 articulated National Park Service operational policies that required, to the fullest extent practicable, the protection, maintenance, or restoration of the natural soundscape resource URBAN PARKS in a condition unimpaired by inappropriate or excessive noise sources ("Soundscape Preservation and Noise Management" Very little recent research has been completed that discusses 20002004). In this Order, an outline of the park director's noise in urban parks; however, it does indicate that noise is responsibilities included natural soundscape preservation as an important urban park characteristic, but not as important part of the operating policies of the park. The Order provided as other criteria, such as safety and cleanliness. Results from a broad structure for consideration of soundscape preservation noise surveys and laboratory listening tests showed that the in the park facilities planning process, but it did not address subject's expectation to hear a sound in a specific environ- specific noise level goals or specific programs. ment influences the corresponding annoyance. Furthermore, the acceptability of the non-natural sound increases with In 2005, the FAA published a report that summarizes the decreasing levels and detectability. These findings are findings of all known aircraft noise (dose) and visitor annoyance significant as they point out that loudness of a noise source is

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17 not the most important aspect of its acceptance. Natural levels were compared with locally permitted levels, and were sounds expected in a park setting are deemed acceptable no classified as "acoustically polluted or unpolluted." Measured matter what their sound level, although unexpected sounds values were also evaluated according to international legisla- such as aircraft and road noise are judged as annoying. tion from Rome, Germany, WHO, and the U.S. EPA. Noise levels in the test parks do not satisfy any of the standards Another evaluation of noise pollution in urban parks was used. The study provides a useful comparison of various in- conducted in Brazil (Zannin et al. 2006). Measured noise ternational noise limits that may be applied to parks.