Yellowstone Soundscapes Program

Yellowstone's soundscape is the aggregate of all the sounds within the park, including those inaudible to the human ear. Some sounds are critical for animals to locate a mate or food, or avoid predators. Other sounds, such as those produced by weather, water, and geothermal activity, may be a consequence rather than a driver of ecological processes. Human-caused sounds can mask the natural soundscape. The National Park Service goal is to protect or restore natural soundscapes where possible and minimize human-caused sounds while recognizing that they are generally more appropriate in and near developed areas. The quality of Yellowstone's natural soundscape therefore depends on where and how often non-natural sounds are present as well as their levels.

Acoustic data have been collected since 2003 as part of Yellowstone's Soundscape Program. Automated systems collected digital recordings and sound levels 24 hours a day throughout the year. Targeted measurements collect acoustic data about oversnow vehicles, motorcycles, motorboats, and other noise sources of interest. The natural soundscape is quantified through analyses of the automated system data. Detailed methods and results are posted annually in the winter use reports.

This map of Grand Teton and Yellowstone shows the 97 locations where long-term acoustic monitoring has occurred since 2002. Thousands of hours of recordings have been collected along with tens of millions of seconds of sound levels. These sites were variously chosen based on management objectives, acoustic conditions, emerging noise issues, and other reasons. By clicking on a site marker a popup window will open displaying the following information- Site Name, Dates of data collection, Acoustic Summary, Photo(s), the Lowest and Maximum sound level recorded, number of hours/days of data, Common Sounds (with % time audible), and Sound Metrics. A few sites indicated with black markers (with more to be added) have recordings that illustrate the typical sounds that can be heard during the day and night throughout the year, and Spectrograms as described below.

How to read Spectrograms

The NPS developed a technique for plotting the 33 one-third octave band frequency decibel levels for each hour of the day. The major sources of sound at each monitoring location can be "seen" in these spectrograms. Each figure is one day, 24 hours from midnight to midnight. Each row contains two hours starting with the first hours of the day, labeled with white two digit numbers. The sound frequency is plotted on a logarithmic scale as indicated in the left margin with high frequencies at the top and low frequencies at the bottom of each row. The bottom margin contains the decibel range and associated colors. Brighter colors indicate higher sound levels;deep blue is the quietest. Not only can specific sound sources be identified from these spectrograms, but patterns and the variability in number, timing, and sources of sounds can be seen.

Last updated: April 6, 2016

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