Helium Speech Unscramblers: A Critical Review

Abstract

Man's attempt to probe and utilize “inner space” have, to a large degree, been hampered by inadequate voice communication. One of the specific sources of speech degradation is the use of helium as an inert breathing gas in the deep and/or saturation, diving situation. In turn, electronic devices have been developed which are designed to improve speech intelligibility distorted by the effects of high ambient pressures and HeO2 breathing mixtures. In order to evaluate the effectiveness of these HeO2 “unscramblers,” the Communication Sciences Laboratory at the University of Florida has undertaken a four-part project: (1) to evaluate available unscramblers on line; (2) to test them off line; (3) to develop a standardized test for evaluating all types of unscramblers; and (4) to establish guidelines for the development of optimum equipment of this type. The present paper will discuss the following: (1) techniques for helium speech unscrambling; (2) protocols necessary to conduct system evaluation properly; (3) development of the standardized off-line test for the evaluation of all types of unscramblers; and (4) results of several on-line and off-line evaluations. Finally, a discussion of the strengths and weaknesses of current approaches to HeO2 speech processing, and recommendations for the improvement of these devices will be presented.