Measurement and modeling of snowmobile noise and audibility at Yellowstone and Grand Teton National Parks

Abstract

The U.S. National Park Service is concerned about the effect that noise from snowmobiles and other over-snow vehicles has on the natural soundscapes in the National Parks. This paper addresses the measurements and modeling performed to assess both the total area in the parks where snowmobile noise would be audible and the noise intrusiveness as a function of distance from the trails. The work was performed in support of an Environmental Impact Statement that evaluated seven operational transportation alternatives in the two parks. The modeling approach computed both A-weighted sound levels and audibility continuous time histories of snow-vehicle noise at several distances from the trails. Acoustical input to the model included 1/3-oct band levels for ambient conditions, vehicle source levels, and propagation of sound over a snow-covered surface. Consequently, distances to the onset of audibility detection, areas of the parks affected, and statistics on received sound levels were calculated. The paper presents both the modeling approach and examples of results.