ACOUSTICAL EVALUATION: COMPARATIVE TESTING OF EXPERIMENTAL OXYGEN MASKS

Three different models of experimental oxygen masks, MSA type E, and one type A-14 mask were tested and compared for acoustic response under experimentally controlled conditions of temperature and pressure. No significant differences were observed in the intelligibility scores of no-chamois, part chamois and full chamois lined, MSA type E, experimental oxygen masks under the following conditions: Sea Level at 5F; 20,000 Feet at -5F; 28,000 Feet at -29F; 35,000 Feet at -42F. The average intelligibility for all three MSA type E masks tends to decrease from 80% at sea level and 20,000 feet to 74% at 28,000 feet, and to 69% at 35,000 feet. The type A-14 mask decreased in intelligibility from 74% at sea level to 57% at 35,000 feet. Three different models of experimental oxygen masks, MRS and the Baldwin mask were tested and compared for acoustic response at sea level. Average intelligibility scores for the Baldwin mask, MRS mask with chamois lining, MRS mask with suede lining and MRS mask with no lining indicate no significant differences. High internal variability in the scores indicate the need for further refinement in the testing conditions. (Author)