specifically to relate oceanOjgraphic research projects to 

 the potential gain in the performance of sonar systems , 

 both present and future . 



If one were to try to draw up a list [Fig. I5] of all 

 possible sonar systems, one possible approach would be to 

 define a "system" as a combination of platform and sound 

 channel. For example, in deep water a submarine using a 

 convergence- zone mode would be a feasible system, but the 

 same system would be unlikely in shallow water. Using 

 this classification scheme — not a unique approach, only 

 convenient — one obtains for active"" sonar 75 possible 

 systems, of which thirty are likely to exist. 



We also divided the possible environmental factors 

 LFig. 16] into those related to Transmission, Reverbera- 

 tion, and Ambient Noise. A more-or-less natural sub- 

 division then occurs, for example, in breaking reverbera- 

 tion into boundary-caused, volume-caused, etc. Finally, 

 a sub- sub division into the oceanographic factors that one 

 might study reveals enough factors to spend one's life 

 pondering. 



From the list of 30 sonar systems and 24 environmental 

 factors we chose the prominent candidates and were then 

 faced with having to define the "payoff" of this game — 

 we decided to assess the importance of a particular 

 environmental parameter on a particular sonar system in 

 terms of the potential benefit to the system likely to 

 be provided by increased knowledge of that parameter. 



For existing sonar systems, the potential benefits 

 are primarily in helping us to understand the various 

 causes of signal degradation, but for future systems 

 improved knowledge of the environment might help us to 

 optimize the design characteristics. For a simple 

 example, improved knowledge of absorption will not help 

 us with our present systems, but if there were some 

 "closed door" of strong absorption at, say, a particular 

 frequency, then we could possibly design a new sonar to 

 ignore that "closed door". 



Note that the presentation here does not use any 

 weighting factors to reflect the relative effectiveness 

 or popularity of the various sonar systems. This is, 

 instead, an attempt to look at the effect of environmental 

 studies on the whole sonar complex and not to tie 



Note the following discussion is only for active 

 systems. 



69 



