Effect of Pressure on Electrodes 



Insufficient evidence has been obtained to form any pos- 

 itive conclusions on the effect of pressure on electrodes. 

 However, several findings can be reported. 



In deep-water tests at Lake Pend Oreille it was found 

 that electrodes that performed very well in many firings at 

 near atmospheric pressure blew to pieces when used at a 

 depth of 300 feet below the surface. An example of this is 

 shown in figure 6. Evidence of many firings can be seen 

 by examining the electrode surfaces. Experience has shown 

 that if water gets inside the electrode it will cause it to 

 explode from within. In the case shown, apparently water 

 penetrated the dielectric material via a small crack when 

 subjected to pressure at this depth. 



In one test, using a gap separation of 1/2 inch, the gap 

 which fired well at atmospheric pressure would not fire 

 when the pressure was increased to 200 psi for the same 

 impressed potential. Decreasing the gap solved the problem. 

 This result would indicate that there is probably a critical 

 gap spacing versus depth, at least in fresh water. This 

 should not be a problem in sea water. 



All the problems of deep submergence appear to be 

 ultimately surmountable, and the underwater spark sound 

 source appears to be well adapted for use in the deep 

 ocean. 



TESTS AND MEASUREMENTS 

 Test Procedure 



Tank Observations 



Pressure and frequency measurements of underwater 

 sound usually have to be made in an open body of water or 

 in specially constructed acoustic tanks. For visual and 

 aural observations, however, a small tank is useful. Two 

 tanks were used in most of the laboratory experiments 

 reported here. The smaller of the two was a modified 

 ammunition box measuring approximately 48 by 40 by 30 

 inches (fig. 7); the larger tank was a modified barge pontoon 

 measuring approximately 5 by 7 by 5 feet. Both tanks were 

 painted white on the inside to provide contrast for photog- 

 raphy. 



