HUMAN BEHAVIOR PROGRAM 253 



UNCOMPLETED STUDIES 



The scientific program of Sealab n was intentionally ambitious. It was anticipated, how- 

 ever, that some of the work planned might not be successfully carried out due to constraints 

 imposed by the situation in general and by the physical environment in particular. Further- 

 more, most of the experiments were being attempted for the first time in an operational situ- 

 ation. For this reason, the following accounts of experiments, which were not completed, are 

 presented. In many instances the reason for lack of completion was primarily one of schedul- 

 ing. It is hoped that such information may provide guidelines for future efforts of a similar 

 type. 



Auditory Threshold and Localization Study 



The purpose of this study was to determine the distance at which various types of sounds 

 could be heard by a diver underwater, as well as to measure his ability to localize the direc- 

 tion. The sounds to be used were a 500 and 5000 cycle pure tone, a series of clicks, and FM 

 chirps. The sounds were prerecorded on tape, calibrated, and fed into three piezoelectric 

 hydrophones placed on the bottom. Although the sound-pressure levels had been calibrated 

 previously in shallow water, the divers were unable to hear any signal at the observer's sta- 

 tion. A microphone, placed at the observer's station, would not pick up the stimulus signals, 

 but was able to pick up verbal instructions recorded on the tape, indicating that the system was 

 working. Apparently, the 50 watts of power utilized was not sufficient. This is undoubtedly due 

 partly to the high ambient noise levels caused by large generators operating on the surface, 

 noises originating in the habitat, masking of sound by the diver's rubber hood, and bubbles. 



Stationary Target Array 



Plans were made to set up ten rectangular visual targets to be viewed by the divers from 

 inside the habitat. These targets were to be arranged so that target 1 was five feet from the 

 port window, target 2, 15 ft, target 3, 25 ft, etc. The first four targets contained four colors: 

 black, white, yellow, and orange. The remainder were half wnite and half black. The purpose 

 was to gather daily data on visibility and to assist divers in planning activities where visibility 

 was a factor. 



The Measurement of Visual Acuity 



Specially mounted eye charts were devised to measure visual acuity. Although it was not 

 anticipated that acuity would change, it was felt that when taken with the other visibility meas- 

 urements, these observations would increase our understanding of visual capability underwater. 



Observation of Minute Organisms 



A special coUimated light source was obtained from the Scripps Institution of Oceanography 

 for the purpose of observing the natural motions of plankton and other minute organisms in the 

 water. It was intended that this unit be placed on the bottom in such a way that the light would 

 point into one of the ports of the habitat. Because the light rays would be parallel, all plankton 

 and other small organisms would be seen clearly silhouetted to anyone looking into the light 

 from the habitat. Not only would this permit the density of the plankton to be estimated, but 

 the characteristics of their motions could be studied as well. 



Television vs Human Visibility 



In cooperation with divers of the U.S. Navy Mine Defense Laboratory, it was intended to 

 compare the detection and recognition capabilities of a diver with those of underwater televi- 

 sion cameras. The plan called for the diver to swim toward a series of targets with his buddy 

 carrying the camera. The detection and recognition ranges of the diver would be compared 



