developed for this purpose. Current meters mounted on floats for 

 use in the deep ocean have already approached this principle. There 

 are other methods. 



We need deep-water sound sources of all kinds. Noise moni- 

 toring at the bottom will be done. A particular need is a cheap 

 sound source that will have considerable energy, such as, an 

 explosive charge, and that will make a sound when it hits bottom. 

 There are very many uses for this kind of a device. 



The most urgently required item is a system for making a 

 low frequency sound -- 20 to 400 cycles --at frequent intervals -- 

 at least each 2 minutes -- of an intensity equivalent to one half 

 pound of TNT, that is safe to operate and does not require too 

 large an energy source. 



shot or hydrophone 



t ronsponde r B 



tro nsponder C 



17.15 



194 



FIGURE 



ACOUSTIC POSITION KEEPER 



