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Systematic measurements, similar to FAR Part 36, were made on eight models of Army rotary-wing aircraft (OH-58, AH-1G, UH-1M, UH-1B, UH-1H, CH47B, CH54, TH-55). The aircraft performed dynamic operations consisting of level flyovers, ascents, descents, turns, takeoffs, and landings; and static operations including in-ground and out-of-ground effect hovers. SEL versus distance curves were developed for these operations. Results are grouped according to model and type of operation and are suitable for use in manual or computerized programs for predicting noise impact for rotary-wing aircraft. Type of maneuver was not found to be a significant factor. The largest level differences are from one type of aircraft to another.

No abstract

Because of Chicago’s dominance as a rail center in the 19th and 20th centuries and the miles of track present, parcels of land available for residential and other noise-sensitive construction frequently lie adjacent to freight, commuter, and Chicago Transit Authority (CTA) tracks. As A-weighted sound levels commonly exceed 105 dBA underneath CTA elevated tracks, special methods of noise abatement for high-rise and other construction to address high noise levels are necessary. Also discussed will be methods of establishing acoustical criteria appropriate for commercial and residential interior spaces.