Eardrum rupture

The ear is a very sensitive and complex organ that responds to very small variations in pressure. It was argued in Hirsch (1968) that ear drum rupture is decisive as to ear damage from blast waves. Figure C-3 shows the percentage of eardrum ruptures as a function of side-on overpressure F,. 

Eisenberg3 reported the following data on the effect of explosion peak overpressures on eardrum rupture in humans ... 

A blast produces a peak overpressure of 47,000 N/m2. What fraction of structures will be damaged by exposure to this overpressure What fraction of people exposed will die as a result of lung hemorrhage What fraction will have eardrums ruptured What conclusions about the effects of this blast can be drawn ... 

Table 2-4 converts the probit to percentages. The result shows that there are no deaths and that less than 10% of the exposed people suffer eardrum ruptures. This assumes complete conversion of explosion energy. 

Range for 1-90% eardrum rupture among exposed population... 

Clearly, this is a sizable e.xplosion. In fact, a blast of 5 kg ofTNT will cause the total destruction of structures not reinforced to withstand blasts within a circle of raciiu 7 meters from tlie blast site, substantial damage out to a radius of 14 meters, minor siructural damage out to 55 meters, and broken windows out to 130 meters. Also, eardrum ruptures can be e-xpected to 10 meters from the site of the e.xplosion. M... 

Eardrum rupture 5 psi incident and maximal overpressure 2.5 psi incident overpressure reflected to give 5 psi maximal overpressure... 

Peak side-on overpressure 0.175 bar (eardrum rupture) - small i... 

The ear consists of three parts the external, middle, and inner ear. The external ear consists of the pinna and the external auditory canal that transmits sound to the middle ear. The middle ear has an air-filled cavity that contains auditory ossicles, which are the malleus, incus, and stapes. The auditory ossicles forward the sound to the inner ear where the eardrum is located. Pressure on both sides of the eardrum is equalized by the eustachian tube that connects to the nasopharynx. The eardrum could rupture if pressure becomes unequal. The inner ear also contains a series of canals called the labyrinths that are made up of the vestibule, cochlea, and semicircular canals. The vestibule maintains equilibrium and balance and the cochlea is the principal hearing organ. 

An explosion is defined in the National Fire Protection Association (NFPA) Fire Protection Handbook as a rapid release of high-pressure gas into the environment. This release of high-pressure gas occurs regardless of the type of explosion that has produced it. The high-pressure energy is dissipated by a shock wave that radiates from the blast center. This shock wave creates an overpressure in the surrounding area that can affect personnel, equipment, and structures (see Figure 3.2). An overpressure of just 0.5 to 1 psi can break windows and knock down personnel. At 5 psi, eardrums can rupture and wooden utility poles can be snapped in two. Ninety-nine percent of people exposed to overpressures of 65 psi or more would die. 

Ruptures of the eardrum are calculated according to Eq. (B.23a), which gives a probit value of... 

Have you ever had a ruptured eardrum or a serious hearing problem ... 

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