UNDERSEA TECHNOLOGY 67 



Voice distortion caused by the helium-oxygen atmosphere used by 

 divers causes many unique problems in communications hardware develop- 

 ment. The human voice in a helium atmosphere assumes a "Donald Duck" 

 quality. This phenomenon becomes more pronounced as the pressure in- 

 creases and eventually makes intelligible speech almost impossible. In an 

 effort to overcome this difficulty, electronic devices have been developed 

 which effect a frequency shift transformation on the voice, adjustable 

 according to depth. Work is continuing in the miniaturization and im- 

 provement of this helium voice unscrambler. 



Navigation for Divers 



Navigation systems are required for divers or diver-controlled vehicles 

 just as in the submersible search operation. To be effective the divers 

 must know where they are, how to get back to their habitat or transfer 

 capsule, and which way to go on a search mission. For the individual 

 diver, navigation can be a matter of Hfe or death, since his breathing 

 apparatus gives him a limited time in the water. Present limitations in this 

 area may force the continued use of tethered divers— a serious restriction 

 on the aquanauts. 



Techniques developed for submersibles approach the accuracy needed 

 for divers— a matter of a few feet. However, submersible equipment is far 

 too heavy and requires too much power. Furthermore, it would be un- 

 realistic to expect the diver to perform significant computations while 

 swimming. For this reason, simple ranging and directional systems will 

 have to be developed that are Hght weight and easily carried by the diver 

 or his support vehicles. 



SATURATED DIVING AND SEALAB 



Until the late 19th century man's efforts to penetrate the ocean depths 

 as a diver were bound to developments in machinery such as diving helmets, 

 diving bells, and air compressors. As divers went deeper and remained 

 longer, their efforts were paced by physiological problems rather than 

 engineering problems. In the 1870's the cause of the "bends," or decom- 

 pression sickness, was diagnosed and a cure proposed: gradual decompres- 

 sion. Other physiological problems arose involving oxygen poisoning and 

 nitrogen narcosis. 



