Outdoor sound propagation

Authors

  • G.A. Daigle National Res. Council, Ottawa, Ont., Canada

Keywords:

acoustic wave propagation, acoustic wave reflection, acoustic wave transmission, aeroacoustics, atmospheric acoustics, atmospheric temperature, atmospheric turbulence, ISO standards, wind, outdoor sound propagation, geometrical spreading, flat hard ground, grass covered ground, snow, reflection coefficient, ground surface, sound source, sound receiver, wind gradient, temperature gradient, temperature lapse, temperature inversion, shadow zones, sound fluctuations, sound transmission, ISO 9613 Part 2

Abstract

The reality of sound propagation outdoors is more complicated than simple geometrical spreading above a flat hard ground. Most common grounds, such as grass covered ground and layers of snow, are acoustically soft. This implies a complex reflection coefficient leading to a measured spectrum that is strongly influenced by the type of ground surface between source and receiver. Grounds may not be flat, leading to shadow zones or alternatively multiple reflections at the ground. Gradients of wind and temperature refract sound either upwards (upwind or in a temperature lapse) or downwards (downwind or in a temperature inversion), also leading to shadow zones or multiple reflections, respectively. Atmospheric turbulence causes fluctuations and scatters sound into acoustical shadow zones. Many of these features mutually interact and accurate predictions of sound transmission from source to receiver must somehow account for all of these phenomena simultaneously. Thus for example, ISO 9613 Part 2 in wide use today, attempts to account for all the phenomena empirically. In recent years the application of numerical techniques has led to significant advances. This plenary will review the various phenomena. Emphasis will be put on field measurements and simple physical interpretations. In a few cases, the predictions of ISO 9613 Part 2 will be compared with physical or numerical models

Published

2004-09-01

How to Cite

1.
Daigle G. Outdoor sound propagation. Canadian Acoustics [Internet]. 2004Sep.1 [cited 2021Apr.12];32(3):12-. Available from: https://jcaa.caa-aca.ca/index.php/jcaa/article/view/1603

Issue

Vol. 32 No. 3 (2004)

Section

Proceedings of the Acoustics Week in Canada

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