Your ear has three main parts: outer, middle and inner. You use all of them in hearing. Sound waves come in through your outer ear. They reach your middle ear, where they make your eardrum vibrate. The vibrations are transmitted through three tiny bones, called ossicles, in your middle ear. The vibrations travel to your inner ear, a snail-shaped organ. The inner ear makes the nerve impulses that are sent to the brain. Your brain recognizes them as sounds. The inner ear also controls balance.
A middle ear infection (otitis media) is the most common cause of eardrum perforation. The eardrum can also be perforated by a sudden change in pressure—either an increase, such as that caused by an explosion, a slap, or diving underwater; or a decrease, such as occurs while flying in an airplane. Another cause is burns from heat or chemicals. The eardrum may also be perforated (punctured) by objects placed in the ear, such as a cotton-tipped swab, or by objects entering the ear accidentally, such as a low-hanging twig or a thrown pencil. An object that penetrates the eardrum can dislocate or fracture the chain of small bones (ossicles) that connect the eardrum to the inner ear. Pieces of the broken ossicles or the object itself may even penetrate the inner ear. A blocked eustachian tube, which connects the middle ear and the back of the nose, may lead to the perforation because of severe imbalance of pressure (barotrauma).