In-flight measures of stress reduction due to wearing expandable foam earplugs

Ten low-time pilots (less than 150 h) who did not normally use earplugs flew three flights each in Cessna-152 training planes. The flight routines were all the same, lasting about 45 minutes. Each pilot flew one flight while adapting to earplugs, another flight with earplugs, and a third flight without earplugs. Pilot's breathing rate was the measure of autonomic arousal. A baseline rate was measured before each flight and in-flight scores were expressed as changes from baseline. Half the pilots flew their flights in the order, with-with-without earplugs and half flew in the order without-with-with. Results showed a mean increase in breathing rate above preflight baseline of 30% without earplugs and an increase of only 21% with earplugs (data taken from second flight with earplugs) for a significant savings of 9% (p less than 0.025, Wilcoxsen matched-pairs signed-ranks test, one tailed).