Measuring Sound

Microphone, weather station, and solar panel in dry landscape with mountains in the background.
Sound monitoring station at Great Sand Dunes National Park & Preserve.

NPS Photo

Note: Some of the PDFs on this page are being converted to meet 508 compliance codes and are temporarily unavailable; they will be re-uploaded upon completion. Contact the division if you require these documents.

If a tree falls in the woods, and no one is around to hear it... it may have been recorded!

Efforts to protect the acoustical environment in our national parks are driven by NPS management policies. But before any action can be taken, park planners and managers need reliable data about a park's existing acoustical environment. What natural and cultural sounds can be heard at the park? What types of human-caused noises can be heard? Where, when, and how often are they heard, and how loud are they?

Through sound monitoring efforts, parks can learn about the acoustical environment as a whole and identify desirable and appropriate sound sources, as well as those that are undesirable in the park setting. Information gathered can then be used to identify the potential impacts of non-natural sounds and proposed developments or actions that may affect the acoustical environment.

Noise modeling software can help to predict how sounds will spread across a park landscape. To learn more about noise modeling, view this presentation by NPS Biologist Katie Nuessly (pdf 2.5MB).

NSNSD summarizes sound measurements taken in national parks in a Natural Resource Report series. Click here to see a list of available reports.

If you're interested in learning how to conduct acoustical monitoring, you can download the Acoustical Monitoring Training Manual (pdf 2MB).

If you work in a park and are interested in technical assistance on a sound-related topic, view this presentation to learn how we can help (pdf 2MB).

Overhead view of an acoustic technician preparing microphone equipment for placement in the field

In the Field

Acoustic monitoring reveals a range of natural and human-caused sounds in parks; scientists use the data to assess park resource conditions.

Spectrogram shows the wave forms of auditory information

Types of Data

Several types of data are needed to accurately quantify the acoustic environment of a park.

Geospatial sound map shows concentrations of sound in areas across the USA

Mapping Sound

Geospatial sound maps reflect measurements of sound in parks as well as urban and rural areas across the USA