Voice fundamental frequency in saturation diving

Abstract

Divers under hyperbaric conditions experience a marked deterioration in speech intelligibility. Included among the possible features that contribute to speech degradation is speaking fundamental frequency (SFF). Based on the physics of the environment and the physiology of the diver, it would not be expected that SFF would vary due to HeO2/P conditions. However, in an earlier pilot study, increase in SFF was found. In order to test the cited hypothesis as well as expand the previous limited findings, a large group of U. S. Navy divers were studied. The diver/subjects produced speech at the surface and at depths of 200, 450, and 600 ft in helium-rich environments. Of the original pool of 46 divers, 28 were studied at 200 ft, 22 at 450 and 9 at 600 ft. The speech material used was the first paragraph of the Rainbow Passage; SFF was obtained by processing this passage by FFI-6. The raw data revealed a significant rise in fundamental frequency to 450 ft and a subsequent decrease at 600 ft, but subsequent analysis (based on the divers' SFF at the surface) showed an almost linear increase in SFF with increases in helium concentrate and ambient pressure. These results are discussed; it is believed that divers' attempts to speak “more intelligibly” (rather than the HeO2 environment) were the cause of this shift. [Work supported by ONR.]