The eardrum (also called the tympanic membrane) is a thin skin-like structure in the ear. It lies between the outer (external) ear and the middle ear.
The ear is divided into three parts – the outer, middle and inner ear. Sound waves come into the outer ear and hit the eardrum, causing the eardrum to vibrate.
Behind the eardrum are three tiny bones (ossicles). The vibrations pass from the eardrum to these middle ear bones. The bones then transmit the vibrations to the cochlea in the inner ear. The cochlea converts the vibrations to sound signals which are sent down a nerve to the brain, which we ‘hear’.
The middle ear behind the eardrum is normally filled with air. The middle ear is connected to the back of the nose by the Eustachian tube. This allows air in and out of the middle ear.