Meteorological Effects on Sound Propagation

Doug Sheadel, B.Sc., CCM
Yong Ma, M.Sc.,P.Eng.
Ji Cao, M.A.Sc.

Abstract
Sound level modeling is usually based on algorithms that assume that the atmosphere is near standard. Some sophisticated models include adjustments that account for downwind or atmospheric stability class. However, sound propagation under strong atmospheric inversions is not consistent with standard algorithms. Therefore, modeling methods tend to underestimate the sound levels at distant receptors under these exceptional conditions. One result of nonstandard propagation is that sound levels from a specific source may be significantly increased at some distant locations. While the conditions that produce the nonstandard propagation might be infrequent, they can be responsible for tension between industrial noise sources and neighboring communities.

The purpose of this paper is to summarize and compare the various effects on sound propagation during conditions of standard and nonstandard atmospheric structure. Common non-standard atmosphere layers are produced by radiation inversions, frontal patterns or downwind conditions. Atmospheric structure principles and the corresponding noise propagation relationships are presented. Questions are raised about the frequency and intensity of the nonstandard noise propagation, and why nonstandard noise propagation can challenge the characterization and treatment of industrial noise problems. The paper also investigates weather products that may aid in identifying areas that are prone to such atmospheric conditions.

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