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
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