NPS Photo - Jared Withers
Many different natural sounds can be heard in Denali National Park and Preserve -- the howling of wolves, the buzz of mosquitoes, the roar of rivers, the thunder of avalanches, the singing of migrant songbirds, the croaking of ravens, and the surreal experience of hearing total silence. The natural soundscape is an intrinsic element of the environment and is highly valued in national parks.
Different habitats have specific soundscape characteristics that are an important attribute of the natural system, with distinct impacts on the human perception of the environment. The natural soundscape is generally comprised of two main sound categories, physical and biological. Physical sounds are created by physical forces (wind, rock fall, rivers, etc.), whereas biological sounds are created by organisms (birds, frogs, plants, etc.). The presence and abundance of sounds from these two categories is used in part to characterize different habitats. Human-generated sounds sometimes negatively impact the natural soundscape and visitor experience.
Soundscape Inventory and Monitoring Program
An important component of the National Park Service mission is to preserve and/or restore the natural soundscapes within national parks. Because the soundscape of Denali National Park and Preserve is becoming increasingly impacted by human-generated noise, a soundscape inventory and monitoring program is underway at the park. Park scientists are systematically documenting natural and human-generated sounds at numerous locations throughout the park including high in the mountains, on glaciers, along rivers, in remote areas, and along the park road.
Currently, park staff are sampling acoustic conditions at as many as 8 new locations per year in an effort to inventory the soundscape of the entire park and investigate areas of special management concern. Automated sound monitoring stations are deployed and collect continuous data for one month, which scientists then analyze and use to compile a representative acoustic profile for that location. This includes the frequency, distribution, and intensity of naturally occurring, as well as human-generated sounds.
Automated sound monitoring stations collect several types of data which allow for the characterization of soundscape conditions. Continuous audio recordings are stored and later played back to a human listener, who identifies what sounds are audible. Sound pressure levels are logged once a second, 24 hours per day, and provide a calibrated measurement of the amount of acoustical energy present at all times. Meteorological data are also stored to ensure measurements are made under appropriate atmospheric conditions.
In depth analysis and discussion of acoustic data collected in Denali National Park can be found in the following annual program reports:
Overflights Advisory Council
The Denali Aircraft Overflights Advisory Council was chartered in 2007 through the Federal Advisory Committee Act with the task of advising the Superintendent, through the Secretary of the Interior, on mitigation of impacts from aircraft overflights at Denali National Park and Preserve. The Council will develop voluntary measures for assuring the safety of passengers, pilots, and mountaineers and for achieving desired future resource conditions. Denali's Sound Program is working intensely to collect and interpret acoustic data so that the Council may make informed recommendations based on good science.
Want to know more?
More information on national park soundscapes can be found at the website for the National Park Service's Natural Sounds Program:
eResource: Denali Soundscapes
Explore data from as many as 30 soundscape study locations in years between 2006 and 2009. Each site provides a summary and descriptions that include GPS location, elevation, ecoregion and sampling period, plus as many as nine charts of specific site findings.
Did You Know?
The vast landscapes of interior Alaska are changing. Large glaciers are receding, permafrost is melting and woody plants are spreading. Comparison of "then-and-now" photographs and data from major vegetation monitoring should allow detection, understanding and potential management of these changes.