Citation

Godin OA. J. Acoust. Soc. Am. 2012; 132(3): 2047.

Affiliation

CIRES, Univ. of Colorado and NOAA Earth System Research Laboratory, Physical Sciences Div., Mail Code R/PSD99, 325 Broadway, Boulder, CO 80305-3328oleg.godin@noaa.gov.

Copyright

(Copyright © 2012, American Institute of Physics)

DOI

10.1121/1.4755528

PMID

22979610

Abstract

Sound speed and especially mass density exhibit large relative changes at gas-liquid and gas-solid interfaces. Sound transmission through an interface with a strong impedance contrast is normally very weak. However, diffraction effects can lead to the phenomenon of anomalous transparency of gas-liquid or gas-solid interfaces, where most of the acoustic power generated by a compact, low-frequency source located within the liquid or within the solid is radiated into the gas. Contrary to the conventional wisdom based on ray-theoretical predictions and observations at higher frequencies, infrasonic energy from compact waterborne and underground sources can be effectively transmitted into air. This paper reviews the theory and emerging experimental evidence of the anomalous transparency. Physical mechanisms responsible for enhanced sound transmission at low frequencies are discussed. The phenomenon of anomalous transparency can have significant implications, in particular, for localization of buried objects and for acoustic monitoring, detection, and classification of powerful underwater and underground explosions for the purposes of the Comprehensive Nuclear-Test-Ban Treaty.

Language: en