THE PROBLEM 



Determine and study those characteristics of the sea 

 floor that affect the propagation of acoustic energy in the 

 sea. Facilitate such studies by specifying what information 

 is needed for a geoacoustic model of the sea floor. 



RESULTS 



1. It was determined that an ideal model of the sea 

 floor in an area of experimental underwater sound propa- 

 gation should include: 



a. A detailed topographic chart based on 

 electronically determined ship's positions. 



b. Information on sub-bottom layering within the 

 upper tens of feet. 



c. Sufficient measurements, from both laboratory 

 and in situ (in boreholes or from submersibles) studies 



to establish the vertical and horizontal variations in those 

 properties of sediments having to do with sound propagation. 



2. Geoacoustic models of certain shallow- water 

 portions of the Bering Sea, and of the site of the 1961 

 Experimental Mohole drilling east of Guadalupe Island, 

 Mexico, were prepared, incorporating new information 

 being used at NEL in studies of underwater sound propaga- 

 tion. These two models contrast strongly; the Bering Sea 

 area has a shallow-water, high-velocity, hard-sand bottom, 

 while the Mohole area has a deep-water, low-velocity, 

 soft-clay bottom. Sediment samples from both areas were 

 tested for sound speed and related properties; laboratory 

 measurements were corrected to in situ values. 



MBL/WHOI 



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