Results 



Acoustic analysis currently is being conducted on these data; however, 

 preliminary findings are as follows: Over a distance of 4000 feet, the sound 

 pressure levels produced by the .38 caliber revolver were 106 db to 110 db; 

 for the M-80 explosives it was 106 db to 121 db (re 0.000 2 dynes/cm^) for the 

 surface and 10-foot depth conditions, respectively. The energy drop (in SPL) 

 between 250' and 4000' ranged from 20 to 31 db. From these data (and data on 

 underwater auditory sensitivity) it appears that explosive sounds of the type 

 studied are only minimally effective as attention-getting devices. That is, 

 the explosive impact and energy levels of these signals at close range are 

 such that they would override any sea or diver regulator noises. However, 

 while audible at distances of over a mile, their levels are low enough to be 

 masked by sea and life support equipment. Finally, due to the short duration 

 of the signal, it appears that explosives are of little value to diver naviga- 

 tion, 



EFFECTIVENESS OF DIVERS WORK WITH AND WITHOUT THE AID 

 OF COMMUNICATION SYSTEMS 



The site of this investigation was Lameshur Bay just off the causeway. The 

 actual test site (as seen from the surface) was approximately that of the skiff 

 seen in Figure 5. 



Figure 5. Site of the "Work Study"; one of the teams may be seen 

 approaching the dive boat. 



The investigation was designed to determine whether a team of divers, aided by 

 underwater communication systems, could accomplish a complex construction task 

 (requiring a high degree of cooperation among them) more effectively than could 

 a similar team without communication. 



X-8 



