This study is an extension and a refinement of an earlier study by the same investigators (3). In the earlier study it was demonstrated that an altitude of 18,500 ft., simulated in a nitrogen dilution chamber, produced a statistically reliable decrement in speech intelligibility under certain conditions of initial difficulty. It was pointed out that the magnitude of the decrement, though not large, was indicative of a change that, under trying conditions, could become hazardous in commercial and military aviation. Though it is common practice to use oxygen above 10,000 or 12,000 ft., a pilot flying at 40,000 to 45,000 ft. breathing pure oxygen has, because of the reduced oxygen tension in the lungs, a physiology which roughly corresponds to that of a man flying at 16,000 to 18,000 ft. without oxygen. The demonstration of a decrease in speech intelligibility in this general altitude range is, therefore, not without some practical significance.It was felt that the effect of altitude on speech intelligibility observed in the previous study would have been greater had some more adequate means been found to equate the difficulty of the test materials used in the altitude runs with those used in the control runs. It also seemed desirable to investigate the possibility of a decrement in speech intelligibility at altitudes somewhat lower than 18,500 ft., the altitude selected in the first investigation. The purpose of the present study was to make such an investigation with improved techniques. * The authors are indebted to the Iinde Air Products Co. for a liberal grant of oxygen and nitrogen, and to Messrs. Mortimer Feinberg and Max Rosenbaum for valued clerical and statistical assistance. ' We are indebted to the RCA Manufacturing Co. and to Mr. W. L. Tesch of the record engineering department for their courtesy. 8 Turntable unit model 199 and pick-up model 209. * Model 87B. 5 Type588A.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.