d) Effectiveness of work by divers with and without voice 

 communication. 



2. Studies Basic to Navigation by Auditory Methods 



a) Basic research in underwater sound localization. 



b) Underwater sound localization of pulses, varying sinusoids 

 and dolphin whistles. 



3. Studies of Diver Retrieval 



a) Acoustic evaluation of M-80 explosives as a function of range. 



b) Acoustic evaluation of 38 cal. pistol shots as a function of 

 range. 



For the purposes of this report, certain of these studies will be discussed in 

 detail; they will include the diver communication systems evaluation (Ic), the 

 work of divers with and without communication (Id), the underwater sound locali- 

 zation experiment (2a and b combined), and the research on recall of divers 

 (3a and b combined) . 



INTELLIGIBILITY OF DIVER-TO- SURFACE COMMUNICATION SYSTEMS 

 AS A FUNCTION OF DISTANCE 



While impressive gains have been made in basic equipment for divers, systems 

 for voice communication are still relatively primitive. Nonetheless, a number 

 of underwater speech communication systems, both civilian and military, have 

 become available to divers. However, so little is known about man's basic 

 ability to speak underwater that the design of these systems has been, of nec- 

 essity, based primarily upon electronic considerations. Moreover, few system- 

 atic or independent evaluations have been carried out. The need remains, then, 

 for an assessment of system efficiency in the transmission of intelligible 

 speech under conditions designed to duplicate actual diver-to-listener communi- 

 cation. The current project is the third in a series of six evaluations we are 

 carrying out on such systems. They are: Diver-to-surface 1) at close range in 

 fresh water, 2) off-shore in salt water--as a function of range (the present 

 study), and 3) in a salt water harbor--as a function of range. Diver-to-diver 

 communication is also evaluated under these conditions. 



Procedures 



The procedures used to gather data for the current diver-to-surface study (over 

 distance) essentially parallel those previously used by our group (see: Hollien, 

 Coleman, Thompson and Hunter, 1970). Basic to the standardization of such 

 underwater procedures is our Diver Communication Research System (DICORS) which 

 has been described by Hollien and Thompson, 1967. For TEKTITE II, we designed 

 a mini-DICORS which was small, lightweight and portable; it may be seen. in 

 Figure 1. For the diver-to-surface study, mini-DICORS was floated at about 

 15 feet in approximately 30 feet of water on the Buck Island range. Hydro- 

 phones were situated at distances of 50, 250, 500, 1000, 2000, and 4000 feet 

 from the diver/ talker o Since depth varied as a function of distance down-range, 

 the hydrophone was placed halfway between the bottom and surface of each location. 



X-2 



