PROSPECTS FOR THE FUTURE 99 



planktology will remain a major part of the Navy's biological 

 research effort; in the deep ocean, these studies will constitute 

 an expansion of this effort. 



It is well known that the presence of marine organisms affect 

 underwater acoustic detection by scattering or reflecting sound 

 or by the masking of wanted signals by soniferous animals. It is 

 not widely appreciated, however, that much of the knowledge of 

 these effects is based upon very few observations in very limited 

 geographic areas. In order to gain a fuller understanding of these 

 effects, substantial expginsion of programs on the acoustical 

 characteristics of marine organisms is required. 



UNDERWATER SOUND 



The growing emphasis on more complex acoustic systems is 

 expected to continue for some time. Modem systems depend 

 heavily on sophisticated computer-oriented refinement of our 

 understanding of the effects of the environment on such systems. 

 Some specific areas are described in the following paragraphs. 



Detailed knowledge of the energy-transfer process near large 

 acoustic transmitters and receivers is required. For radiation 

 at very high sound powers per unit area, water-compressibility 

 effects become significant, and the transfer process becomes 

 nonlinear. In some cases, equipments are so large that environ- 

 mental conditions are not uniform over the entire area of the 

 radiating face. The effects of these nonuniformities must be 

 understood to insure maximum efficiency of systems. 



Detection and communication systems of very large range are 

 conceptually feasible. The cumulative effect of the ocean on 

 sound transmission at long ranges must be determined in greater 

 detail, and methods to predict performance in all of the ocean 

 basins must be derived. 



Effective achievement of the gain possible by using advEinced 

 signal-processing techniques requires much greater detail on 

 signal structure, both desired signals and noise. For older 

 systems, crude knowledge of frequency spectrum and amplitude 

 sufficed, but in the future we must fully understand the total 

 signal statistics and their environmental modifications. 



