Analysis of ambient data measured in the National Parksunder high-wind conditions

摘要

The Federal Aviation Administration and National Park Service are developing air tourmanagement plans to mitigate or prevent significant adverse impacts, if any, to national parkresources. Noise impacts must be characterized relative to representative baseline ambient soundlevels. Computing the representative baseline ambient sound level is not straightforward -methods must be evaluated prior to implementation. This paper summarizes the evaluation ofcurrent treatments of data measured under high-wind conditions. Currently, data with associatedwind speeds greater than 5 m/s, which may contain measurement system contamination, areremoved from the ambient computation. Since the intent is to characterize the entire ambientsound environment, including wind-driven, natural sound sources, some contamination may betolerable. The high-wind data measured at ‘barren’ sites, where the contamination might easilybe identified, were analyzed to determine 1) the characteristics of the contamination, and 2) if aportion of this data be used without significantly affecting the computed ambient. Analysisconfirmed that contamination begins to affect measured sound levels above the 5 m/s wind-speedthreshold, and the contamination can not be definitively identified and removed from thenaturally-occurring sounds. In addition, allowing 10% high-wind data into the dataset does notsignificantly increase the computed ambient.