Acoustical and noise control engineering practitioners of all types regularly test and report on sound emissions and imissions with little or no regard to the uncertainties involved, or even how any such identified uncertainties are to be treated or combined collectively or even quantified. This paper is a synopsis of selected elements of acoustical uncertainty, intended to be a sobering reminder to all practitioners of our inability to precisely define source sound power, to accurately model either single or complex sources, or to precisely model the far field propagation of sound emissions. Further, several seldom considered aspects of uncertainty are addressed, such as a) the careless omission of the Confidence Interval being employed whenever uncertainty is addressed at all, b) the inevitable upward creep in sound level resulting from multiple source uncertainties and c) the often overwhelming influences of atmospheric and vegetation inhomogeneities. The proper methods for combining these several elements of uncertainty are reviewed, in terms of laboratory or field measurements or in the modeling of complex sources.
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