Excessive noise can lead to decrements in performance, impaired verbal communication, fatigue, and hearing damage. On the STS-40/SLS-1 mission noise levels were evaluated through the use of a questionnaire and two objective measures−in-flight sound level measurements and pre- and post-flight crew audiometry tests. Sound level meter measurements suggested that noise levels in Spacelab during nominal operations were approximately 70 dB (A-weighted). This is in excess of the current acoustic specification of 59 dB (A-weighted). Noise measurements conducted in the Orbiter did not exceed current Shuttle standards. Crewmembers recommended that noise levels be reduced. Post-flight audiometry tests indicated that transient decreases in hearing ability had taken place during the mission. The average decrease in hearing level of 4.34 dB was statistically significant. Crewmembers noted that sleep, concentration, and relaxation were negatively impacted by high noise levels. Communication was also hampered. The higher than desirable noise levels in Spacelab were attributed to flight specific payloads for which acoustic waivers were granted. It is recommended that current noise levels be reduced in Spacelab and the Orbiter Middeck. Levels of NC 50 are recommended in areas where speech communication is required, and NC 40 in sleep areas−in accordance with current Space Station Freedom standards. [This research was supported by the National Aeronautics and Space Administration under Contract No. NAS9-17900.]

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The maximum forces that men and women were capable of applying to emergency exit release handles under various conditions were determined. Experiments were conducted on both port and starboard sides of a cabin mockup simulating the interior of the Convair 240. Approximately 339 determinations of the maximum force that 17 female subjects were capable of applying to emergency exit handles were obtained. This study was extended to include measurement of the resultant force and its direction with 112 tests conducted by eight female subjects, of which three participated in the above series. In addition 162 tests were conducted by nine male subjects, and a few tests on six children. The effects of handle configuration, location, position of the subject, and the duration of the muscular contraction are discussed.

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