This paper reviews research on the effects of mechanical noise and natural sound on visitor experiences in national parks. Three approaches to studying noise impacts are described. Most noise research to date has addressed the impact of air-tour overflights on visitor experiences. these impacts are localized with significant percentages of visitors in some parks reporting interference with natural sounds from aircraft noise. Research also shows that unthreatening natural environments can have significant stress-reducing effects for many people. However, it is unclear if these effects are due to hearing the sounds of nature or to a combination of hearing and seeing nature.
Gramann, Dr. James; National Park Service; and U.S. Department of the Interior, "The Effect of Mechanical Noise and Natural Sound on Visitor Experiences in Units of the National Park System" (1999). All U.S. Government Documents (Utah Regional Depository). Paper 428.