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Atmospheric Effects in ISO 9613-2

This paper describes how refraction by wind, temperature, and humidity gradients in the atmosphere can dramatically impact sound propagation and therefore play an important role in determining annoyance from noise emissions. When refraction is upward, lower annoyance is expected because the sound energy is directed away from ground-based receivers. Downward-refracting conditions, on the other hand, tend to raise near ground sound levels and therefore potentially lead to higher annoyance. Besides refraction, the atmosphere produces other important effects on sound propagation, such as temperature and humidity dependent absorption, scattering of sound energy into refractively and topographically formed shadow regions, and random variations in received sound levels. Although the basic physical mechanisms affecting sound propagation in the atmosphere are thought to be well understood, it has proven difficult to develop and agree upon comprehensive, workable engineering approaches to quantify the propagation effects. Among the many reasons for this state of affairs, perhaps the following are most important: (1) many complex interacting phenomena affect the propagation, and it is exceedingly difficult to develop good models for these phenomena working in conjunction. For example, although good theoretical solutions exist for sound diffraction over a barrier in a homogeneous atmosphere, in practice these solutions have limited applicability because of interaction of the atmospheric flow with the barrier, varying ground surfaces in the vicinity of the barrier, etc; (2) for all but very simple scenarios, the physical equations governing the propagation cannot be practically solved across a broad range of frequencies, even with modern computational capabilities; (3) the structure of the real-world environment (atmosphere, terrain, and man-made objects) is quite complicated and cannot typically be characterized with the resolution necessary to predict propagation accurately; and (4) the atmosphere varies over time scales from seconds to seasons (and longer), and therefore it is difficult to extrapolate or generalize the results of a few calculations

Language

  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; References;
  • Pagination: pp 851-860
  • Monograph Title: Noise-Con 04. The 2004 National Conference on Noise Control Engineering

Subject/Index Terms

Filing Info

  • Accession Number: 01054362
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Jul 27 2007 7:06AM