A REVISED STATISTICAL-ANALYSIS OF BLAST SOUND-PROPAGATION

As is well known, sound propagation over long distances is greatly inf luenced by the land surface and weather conditions. Sound velocity var ies with weather conditions, primarily air temperature and wind veloci ty. Schomer et al. presented a rather coarse statistical analysis of C -weighted sound exposure levels from blast sounds propagated over dist ances along the ground ranging from 3.2 to 24 km in a 1978 article in J. Acoust. Soc. Am. The purpose of that analysis was to enable the pre diction of C-weighted day-night average sound levels in the vicinity o f Army installations. The present article contains an improved statist ical presentation of the 1978 data. In this new presentation, all of t he data at each distance (including sound exposure levels too low to b e measured) are treated as if they were part of two normal distributio ns; a higher- and a lower-level distribution. The mean values of the s ound exposure levels and the standard deviations of the two distributi ons are described by equations which can be used to predict C-weighted sound exposure level (CSEL) received in a community from distant blas t sound sources. Because the distributions are Gaussian, one can predi ct the ''energy-averaged'' CSEL, or some more complicated acoustical m easure, from the means, the standard deviations, and the percentage of blast sounds belonging to the higher-level distribution.