Evaluation of Small Arms Noise in a Natural Soundscape – Bear Butte, SD

摘要

Most studies on soundscape intrusion have been limited to moving sources. Of less concern isnoise from small arms. Potential impact was predicted from a proposed large small arms facilitywith 10,000 rounds or more per day on the natural soundscape at Bear Butte, one of the mostsacred sites of the Northern Cheyenne and other tribes. The primary impacted activity ismeditation and oneness with the natural environment that can continue for several days thoughday and night. Non-natural sources included limited vehicles on a nearby highway and farmequipment, but few aircraft. Second-by-second ambient octave band readings were taken at 20sites starting before sunrise. The minimum ambient level observed was 19.6 dBA but limitswere encountered with a ½” microphone. Sound level data on small arms were projected fromthe proposed range four miles north of Bear Butte to elevated points on the Butte assuming azero wind environment. Impact was evaluated using audibility, intrusiveness and impulseweightedDNL. Projected levels were well above ambient. While the DNL was projected toincrease by 15 dBA, this metric has little meaning for this type of activity. Assumptions relatedto outdoor sound propagation, audibility and impulsive noise perception are discussed.