Definition
A thin, taut membrane at the end of the ear canal that vibrates in response to sound waves and pressure changes, transmitting those vibrations to the small bones of the middle ear. It also forms the boundary between the outer ear and the air-filled middle ear cavity, so any difference in pressure between those two sides pushes the membrane inward or outward.
Plain English
A thin layer of tissue inside your ear that picks up sound and also feels changes in air pressure. It separates the outer ear from a small air space behind it, so when the pressure on one side doesn't match the other, the eardrum gets pushed in or out.
Context Anchor
Seen in aviation physiology discussions about the ears, especially when explaining pressure changes during climbs and descents and how the ear helps with hearing and balance.
Derivation
From 'ear' plus 'drum' -- named because the membrane is stretched tight like the skin of a drum and vibrates the same way when struck by sound or pressure.
Why Pilots Care
During climbs and descents, the air pressure outside the eardrum changes faster than the pressure inside the middle ear can equalize. If the pressures don't equalize (often due to a head cold blocking the eustachian tube), the eardrum gets stretched, causing pain, muffled hearing, or in severe cases injury. This is why pilots are taught to clear their ears and avoid flying with congestion.
Grounding Statement
On descent, the outside air pressure increases, and your eardrum may feel pushed inward until the pressure behind it catches up.
Intuition Check
Do not assume the eardrum is the part of the ear that senses turning or motion. The eardrum mainly helps with hearing and pressure; the balance organs are deeper inside the ear.
Example Sentence 1
On descent, the pilot felt pressure building against the eardrum and swallowed several times to equalize.
Example Sentence 2
Sound from the radio headset reached the eardrum and was passed along to produce clear audio.