446 



INTRODUCTION 



Figure 6. Wake of USS Moale (DD 693) as ship turns at 30 knots. 



time suggested that attacks on submarines could be 

 made by detecting the wake and then following it 

 until the submarine was reached. This suggested pro- 

 cedure turned out to be impractical, owing to the 

 very low scattering power of the wakes behind slow, 

 deep submarines. The wake laid by a surface vessel 

 reflects sound so strongly and so persistently that 

 acoustic methods might possibly be useful for at- 

 tacks on such enemy vessels. Obviously a knowledge 

 of the scattering and absorbing power of wakes at 

 different ranges behind a vessel, and at different 

 depths below the surface, would be very useful in the 

 design of equipment" for such methods of attack. 



26.3 ACOUSTIC WAKE RESEARCH 



The aim of current wake studies is twofold: (1) to 

 explore the overall acoustic properties of wakes with 

 a view to possible tactical applications, and (2) to 

 advance fundamental research on the structure and 

 physical constitution of wakes. The second problem 

 may seem rather academic to those who are prima- 

 rily interested in the first one. But many questions 



about wakes presented by naval tactics cannot be 

 answered satisfactorily, at present, for lack of a 

 thorough understanding of the physical constitution 

 of wakes. Thus in the long run, fundamental re- 

 search is indispensable for developing a comprehen- 

 sive doctrine of the use of wakes in naval warfare. 



The solution of that fundamental problem in itself 

 largely depends on acoustic measurements. Since 

 wake research is still in an early stage, and since only 

 incomplete observations are at hand, it would be im- 

 practical to insist upon strict separation of these two 

 aims. Experimental data frequently are relevant from 

 the point of view either of tactical applications or of 

 fundamental research. Accordingly, a certain shift 

 back and forth between practical and theoretical em- 

 phasis is unavoidable. 



In order to plan, execute, and interpret acoustic 

 measurements on wakes, some working hypothesis 

 concerning the nature of acoustic wakes must be 

 used as a starting point. Three physical explanations 

 of the causes of scattering and absorption of sound in 

 the sea have been suggested. The scattering and 

 absorbing centers have tentatively been identified 



