News

This year the National Park Service (NPS) celebrates its centennial, having been established by the passage of the Organic Act†in 1916. According to the Organic Act, a main purpose of the NPS is to conserve parks, monuments, and reservations†in such a manner that will leave them unimpaired for the enjoyment of future generations.â€

Since 1916, it has become increasingly challenging to conserve the acoustical environment, or soundscapes,†of NPS properties. When considering the development of a new project near an NPS-managed property, the potential impact to the acoustical environment will need to be examined using an approach that considers the natural soundscape which is somewhat atypical relative to most environmental noise evaluations in the U.S. Unlike typical state, county, or municipal noise laws around the U.S., which often include quantitative limits to the environmental sound level, the NPS Soundscape Management policy simply states that the NPS will preserve, to the greatest extent possible, the natural soundscapes of parks.†(See Section 4.9 of NPS Management Policies 2006 PDF.)

In order to preserve natural soundscapes, acoustical environmental impacts need to be minimized, possibly to a far greater extent than would be the case to meet a municipal sound level limit. In a quantitative sense, this means limiting or possibly eliminating increases to existing ambient sound levels.

Ambient sound levels in some National Parks could be very low during the nighttime, so preserving the natural soundscape could be quite challenging. Quantifying the existing ambient sound levels typically requires an ambient sound level survey. If the survey needs to take place on NPS land, a permit could be required to gain access to a measurement site (such as a campground) and set up sound level measurement equipment for a period of several days.

For projects where a survey has not been or cannot be conducted, the NPS has developed a rather unique workaround. For roughly the last two decades, the NPS has been measuring long-term ambient sound levels at many of their properties. The result of this effort was summarized in a May 2014 article in the Journal of the Acoustical Society of America (JASA) by Daniel Mennitt, Kirk Sherrill and Kurt Fristrup. Utilizing over 250,000 hours of ambient sound level meas...