Monitoring Reveals Park Enjoys Exceptional Quiet

For the past six years, the Natural Resource Program Center’s natural sounds program has collected acoustical data in nearly 50 national park units. 

An important part of that effort involves calculating the natural ambient for each park, which, pursuant to NPS Management Policies, is defined as the sound level that exists in the absence of human-caused noise.

During this period, program staff have captured some of the quietest places in the United States, including the area inside the crater at Haleakala National Park, where the natural ambient was so low it exceeded the sensitivity of monitoring equipment and reached levels so quiet that you could almost hear the blood coursing through your veins.

Recently, at the request of Great Sand Dunes, program staff deployed an acoustic monitoring system in the northwest corner of the park to characterize current existing ambient sound levels and calculate natural ambient sound levels. The system collected continuous sound pressure levels in decibels and digital recordings  from September 24th to October 10th.  

Much to the surprise of researchers, this monitoring led to the discovery that that the acoustic environment in Great Sand Dunes was exceptionally quiet and  revealed natural ambient levels that rivaled those in the Haleakala crater. As such, this site ranks as one of the quietest locations ever monitored by the natural sounds program. 

Acoustical environments, or soundscapes, which have ambient noise levels that are this low are not only rare, but also extremely vulnerable to noise impacts from a variety of sources. A high sensitivity microphone will be employed in future monitoring at the park in order to more accurately measure the extremely low sound levels of the park.  

The natural sounds program’s acoustic monitoring protocols have recently been posted to our intranet website.  To access a copy, click on the link below.