Diver-to-Diver Speech Intelligibility of Underwater Communication Systems

Abstract

The purpose of this research was to evaluate speech intelligibility of underwater diver-to-diver communication systems. To accomplish this, a second DICORS was designed for two diver/listeners, who could respond to speech produced by a diver/talker situated in the original DICORS. The research was conducted in 30 ft of water at NRL's Underwater Sound Reference Division's Bugg Springs facility. Speech materials consisted of Clarke multiple-choice lists; responses were recorded on an IBM keypunch, at the surface, coupled to specially constructed multiple-choice response switches activated by listeners. Five experienced diver/talkers and up to eight experienced diver/listeners (the average talker/listener totals were 36) were situated 30 ft apart and back to back. All systems evaluated were rigged with the Bioengionics “Nautilus” muzzle and a double hose regulator. Several units could not be kept in operation, however, and that equipment could not be evaluated. Mean scores for the other four units ranged from 57% to 64%. Our scares are higher than those previously reported for these units under diver-to-surface protocols; however, they probably reflect (1) experience with this type of research of both talkers and listeners, (2) the use of multiple-choice word lists (which elevate scores) instead of PB25 word lists, and (3) use of the Nautilus mouthcup and a double hose regulator (which has been shown to be the optimum available support configuration). In any case, it can be concluded that (1) while reasonably good diver communication systems are available, they are not yet of sufficient quality to allow for adequate underwater voice communications, and (2) no single approach (modulated, hardline, acoustic) is currently superior to the others. [This research was supported by Physiological Psychology Branch of the Office of Naval Research.]