The Physics Factbook™
Edited by Glenn Elert -- Written by his students
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|Cameron, Skofronick, Grant. Physics of the Body. Medical Physics Publishing, 1992, 1996: 123.||"A pressure differential of 17 kPa (120 mmHg) across the eardrum, which can occur in about 1.7 to 5.3 ft of water, can cause the eardrum to rupture."||17 kPa|
|Fraser, Thomas M. The Worker at Work: A Textbook Concerned with Men and Woman in the Workplace. CRC Press: 323.||"The eardrum can rupture at a differential pressure of 5-10 psi across the drum"||35–69 kPa|
|Stewart, Charles. Blast Injuries: Preparing for the Inevitable. Emergency Medical Practice. Vol. 8 No. 4 (April 2006).||"At a pressure of about 35 kilopascals (5psi), the human eardrum may rupture". With an overpressure of 100 kilopascals (14 psi) almost all eardrums will be ruptured.||35–100 kPa|
|Richmond DR, Yelverton JT, Fletcher ER, Phillips YY. Physical correlates of eardrum rupture. Annals of Otology Rhinology, and Laryngology. Vol. 109 (May 1989): 35-41.||"A P50 for humans of 100 kPa and a threshold of 35 kPa has been used widely in blast criteria. A recent study suggest a threshold (P1) of about 20 kPa, and gives the overpressures required to produce minor, moderate, and major eardrum ruptures."||20 kPa|
|Alt, Leonard; Forcino, Douglas; and Walker, Richard. Medical Consequences of Nuclear Warfare. Office of the Surgeon General Department of the Army, United States of America (1989): 7.||"Injuries resulting from the blast waves will be caused by exposure to high pressures with very short rise times, and will consist primarily of internal injuries. For example, the threshold level for rupture of the eardrum is about 5 psi."||35 kPa|
The eardrum is a thin, oval layer located deep in the ear canal. It is also known as the tympanic membrane. It helps protect the middle and the inner ear. The eardrum receives vibrations from the outer ear and transmits them to the middle ear. Because it is so thin, the eardrum can be ruptured or punctured. Pressure is one factor that can damage the eardrum. If the air pressure in the ear canal from the outside and the air pressure in the middle air are unequal, the eardrum can be damaged.
Pressure is the force per unit area applied on a surface in the perpendicular direction. The equation for determining pressure is
P = F/A
P is pressure
F is force and
A is area
Pressure is measured in pascals. A pascal is equal to a newton per square meter.
[Pa = N/m2]
The eustachian tube connects the middle air and the nose. It helps to maintain equal pressure on the both sides of the eardrum. When the pressure outside changes suddenly, air moves through the tube to equalize the pressure in the middle ear. If the Eustachian tube is blocked or partially blocked because of an infection, cold, allergy or scarring, air can no longer enter or leave the ear. The pressure difference may cause the eardrum to rupture and bleed. If the difference is great, the entrance to the middle ear will rupture. The tympanic membrane can only withstand a limited amount of pressure. The eardrum may rupture at pressures above 35,000 pascals or 35 kPa.
Shemika White -- 2007
|Beveridge, Alexander. Forensic Investigation of Explosions. Boca Raton: CRC Press, 1998: Page 41.||"It has been established that temporary hearing loss could result with an overpressure level lower than 1 psi, and threshold eardrum rupture could occur at an overpressure of 5 psi; at 15 psi overpressure the rupture rate would rise to 50%."||103 kPa|
|Stewart, Charles. Blast Injuries. Colorado Springs: Charles Stewart & Associates, 2006: Page 33.||"At a pressure of about 35 kilopascals (5 psi), the human eardrum may rupture. With an overpressure of 100 kPa (14 psi) almost all eardrums will be ruptured."||100 kPa|
|URS Corporation. Guidance Protocol for School Site Pipeline Risk Analysis. Austin: URS Corporation, 2007: A-1.||" Lee's Chapter 17, p.237
50% probability of eardrum rupture at peak overpressure of 6.3 psi
90% probability of eardrum rupture at peak overpressure of 12.2 psi"
|Richmond DR, Yelverton JT, Fletcher ER, Phillips YY. Physical correlates of eardrum rupture. New Mexico: Division of Life Sciences, Los Alamos National Laboratory 1989: Page 140: 35-41.||"A P50 for humans of 100 kPa and a threshold of 35 kPa has been used widely in blast criteria."||100 kPa|
|Gesswein, Joseph ; Corrao, Paul. The Position of Eardrum Rupture and Hearing Loss in the scale of Injuries from Nuclear Blast. Bethesda: Naval Ship Research and Development Center, 1972: Page 36.||"The scanty data available on human eardrum rupture from blast pressure suggest a normal distribution of rupture about a median overpressure of 15 psi."||103 kPa|
A ruptured or perforated eardrum is an opening in the tympanic membrane (eardrum). The ear is a sense organ that is used to detect sounds. The ear is used to receive sound and to establish a sense of balance. Like any other organ, the ear is susceptible to injury and is vital to the owner’s survival.
The ear is separated into three main parts; the outer ear, middle ear, and the inner ear. The outer ear consists of the pinna, ear canal, and the surface of the ear drum. The pinna (auricle) is very easy to damage because of the lack of blood supply to the area due to it being mostly cartilage. Meanwhile, the middle ear has three ear bones: malleus (hammer), incus (anvil), and stapes (stirrup). In addition, the inner ear contains two parts: the cochlea which is an organ used for hearing and an organ that senses gravity and motion which is called the vestibular apparatus. The general frequency range in which humans can hear is 20 Hz to 20 kHz.
There are many causes for rupturing an eardrum and they include but are not limited to: blasts, constant loud noises, and pressure from swimming deep. A typical overpressure required to guarantee a rupture to an eardrum would be about 100,000 pascals or 100 kPa. Since eardrum rupture tests cannot be performed on humans, the numbers for blast induced eardrum rupture have been almost theoretical and are more available for animals. The numbers used to predict injury were discovered by clinical experiences, rather than from experiments.
William Wong -- 2007
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