The Federal Aviation Administration’s Office of Environment and Energy (FAA/AEE) with support from the Acoustics Facility at the John A. Volpe National Transportation Systems Center has developed a detailed methodology for characterizing ambient noise in low-level environments such as the National Parks. The presentation will include a general overview of the method, along with a brief historical perspective. Specific details of characterizing a study area’s ambient noise will be outlined, including measurement site selection, instrumentation, and general field measurement procedures. Particular attention will be given to the data reduction and analysis methodology, including guidance on assigning actual measured ambient noise to specific locations within a study area. In addition, several examples of how this methodology has actually been utilized in a practical field measurement application will also be discussed.