SURVEYING THE OCEANS (OCEANOGRAPHIC) 



51 



DEEP 

 REFRACTED 



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Sound propagation paths are 

 determined by use of modern 

 instruments. 



Energy from a sound source in the near-surface region of the 

 ocean follows many diverse paths, which may be generally grouped 

 into the following modes of propagation: 



1) Surface duct — sound which travels in the near-surface region. 



2) Bottom bounce — sound which is reflected off the ocean floor. 



3) Convergence zone — sound which travels along a deep 

 refracted path. 



Older types of sonar relied entirely on the surface duct or direct 

 mode of sound propagation. Thus, much of the environmental data 



