Sound Propagation in the Atmospheric Boundary Layer

The variability of sound propagation in the atmosphere has actually long been recognized. King (1919; see also the account by Beyer [1999]) refers to the “…capricious behavior of sound-waves propagated in the open atmosphere [which] has been attributed to the existence of innumerable discontinuities of temperature, density and humidity, and to refraction by gradients of wind-velocity.” Recordings by Ingard (1953) showed random variations in sound levels of 10-20 dB, which he attributed to the gustiness of the wind. Recent advances in the simulation of atmospheric turbulence and sound propagation enable dramatic visualizations of the variability identified by Ingard. [To view visual recordings visit: http://wp.me/p4zu0b-Qq] Modern long-term experimental studies further demonstrate the challenge of predicting sound levels from atmospheric observations that are typically available in practice (e.g., Konishi and Maekawa, 2001; Valente et al., 2012).