Natural Sounds Program

Spectrograms

Coming in 2009:

For nearly two decades the National Park Service and its contractors have conducted acoustical monitoring at park units throughout the United States. Most of this data has never before been widely accessible to the public, and the Western Soundscape Archive will make available more than 5000 spectral images from over 100,000 hours of park service sound level monitoring.

Each spectral image, or "spectrogram" is a 24-hour picture of the sounds of an area. The images allow rapid visual assessment of daily acoustic patterns and show the prevalence of many kinds of sound sources, such as aircraft, bird songs, insect choruses, rain, wind, river flows and the environment in general. Such sound signatures can offer clues about an area's biodiversity and ecological health, and are also a window into the increasing impacts of human-caused noise on the environment.

See example spectrograms below. Click to enlarge.

	An annotated spectrogram courtesy of the National Park Service.
	This is an example of a 24-hour picture of sounds from Pasture Wash, Grand Canyon National Park. Selected aircraft overflight events are annotated. The Park Service has also identified the sounds of a coyote chorus at approximately 0230 and the dawn chorus of birds that extends from approximately 0500 to just after 0800.
	Each spectrogram will be presented in two different forms. One version, such as the spectral image in this example, represents sounds that are heard within the range of human hearing. The other version (see slide below) shows the full spectrum of the recording.
	An “unweighted” spectrogram not corrected for human hearing.