WEINSTEIN: EXPLOSIVE SOUND-SOURCE STANDARDS 



bubble is there oscillating, I would think you are still going to have 

 an oscillatory spectrum. 



Most likely you would cut off the level of the high-frequency end of 

 your spectrum as you cut off the top of your sharp shock. So you have 

 lost energy at the high-frequency end. You may not have lost as much 

 energy at the low-frequency end as at the high, but possibly some is 

 lost there as well. As I see it through my cloudy glasses, the problem 

 is that so long as you have an oscillating bubble you don't have a white- 

 noise spectrum, and I don't see how you can remedy this with chemical 

 composition alone. 



Dr. G. B. Morris (Scripps Institute of Oceanography) : I believe 

 the oil industry has had this problem of bubble pulses for several years 

 and has in the past few years effected quite a number of solutions. 

 One such system uses injections of high pressure steam, such that the 

 steam condenses into water, eliminating the oscillating gaseous bubble. 

 Other systems make use of what is known as a "sleeve exploder." A 

 propane-oxygen mixture is injected into a perforated tube covered by a 

 rubber sleeve . Upon detonation the sleeve contains the gaseous products 

 which after full expansion are vented to the surface to prevent the 

 bubble pulse. 



Devices like these might get away from the bubble problem, although 

 I suspect these devices give a lower energy output. The signal-to-noise 

 ratios will be lower, and the resulting propagation measurements will be 

 subjected to the signal-to-noise ratio problems discussed by Dr. Weinstein. 

 What you have gained at one end by eliminating the bubble, you have lost 

 at the other end by having a lower energy output source. However, it 

 might be worthwhile examining the outputs of some of these sources. 



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