The relation between eardrum failure and blast-induced pressure variations.

Abstract

During a series of field and laboratory experiments designed to study overall blast effects, incidental observations were made of the ears of more than 490 animals to determine eardrum failures associated with exposure to ‘atypical’ and ‘typical’ blast wave forms. Animals positioned inside structures were exposed to a variety of ‘atypical’ blast waves, whereas those located inside shock tubes or in the open, when high explosives were detonated, were exposed to fairly ‘typical’ wave forms. When the incidence of eardrum rupture is related to the various elements of the measured pressure-time curves, the association is not the same for the two types of wave shapes. Besides suggesting that tolerance is higher for ‘slow’-than for ‘fast’-rising wave forms, the findings demonstrate a wide variability in the magnitude of the overpressures required to rupture the eardrum. Within the limits of the data available, the quantitative differences are noted and discussed with emphasis on the apparent wide variability in tolerance and a proposed explanation for this finding. Although the results are limited strictly to the mammalian species studied, it is likely that the eardrum of man also is sensitive to the shape and character, as well as the magnitude and duration of the blast wave. The data are useful to military and civilian physicians, industrial otologists and all other health and safety personnel including those who have research interests in establishing quantitative dose-response criteria for individuals exposed to blast-induced variations in pressure.