THE ACOUSTIC BOMB 



It is frequently desired to make sound transmission studies 

 in the deep ocean. Because there are few sources that can 

 generate substantial power, particularly in the very low fre- 

 quency region below 1000 c/s, chemical explosives of various 

 sizes are used for the study. This is not only a costly process, 

 but involves considerable hazards. 



The pneumatic sound source is ideal for use as a sound 

 bomb. It is safe, cheap to produce, and creates a substantial 

 sound level at essentially a single low frequency which can be 

 controlled. The sound pressure generated is a function of 

 wall material and thickness. The frequency generated is a 

 function of the depth at which the source is operated and of 

 its initial physical dimension. 



The first model of the acoustic bomb consisted of a very 

 simple pressure mechanism, a small cartridge of carbon 

 dioxide, and a small length of surgical rubber tubing sealed 

 off at the end (fig. 35). This mechanism worked satisfactorily 

 to a depth of about 150 feet. 



Later versions of the acoustic bomb consist of Mark 15 

 Mod 0, practice depth charge pressure mechanisms attached 

 to flasks of compressed air or carbon dioxide, combined 

 with specially designed elastic spheres of various sizes. 

 Figure 36 shows one type used. 



OTHER NOVEL SOUND SOURCES 



CONVERSION OF HEAT TO SOUND 



With the advent of nuclear submarines there is an 

 abundance of heat available which might be utilized in 

 the generation of sound. A few simple experiments 

 involving the principle of converting heat to sound were 

 conducted as part of the Novel Sound Sources program 

 and are reported briefly as a possible impetus to others 

 to continue this approach. 



Carbon dioxide, or dry ice, at a critical point about 

 -110°F, changes state from a solid to a gas. This 

 phenomenon is known as "subliming. " If a metal object 

 which is at or near room temperature is brought into 



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