Noise Data from Snowmobile Pass-bys: The Significance of Frequency Content 2002-01-2765
This paper presents a summary of the results of noise measurements of various snow machines conducted by Harris Miller Miller & Hanson Inc. (HMMH) in 2002. Because the data were collected as part of an analysis including audibility and sound propagation over long distances in national parks, measurements included the frequency content of the snow machines as well as the A-weighted sound levels (dBA). Frequency data are given for some of the snow machine pass-bys at the SAE Clean Snowmobile Challenge 2002 and also for those measured under various operational conditions at Yellowstone National Park in February 2002. Measurements were conducted in substantial conformance with SAE J192. Comparisons are made of snow machines under acceleration and constant-speed conditions, and between those with two-stroke and four-stroke engines. The data show substantial differences in spectral content for some vehicles with similar A-weighted sound levels. A description of the significance of low-frequency tonal content on the audibility of noise in remote areas provides context for the spectral data presented.