Sound travels through the ear canal to the eardrum via the air conduction process, causing the eardrum to vibrate. These vibrations are passed to three smaller bones in the middle ear called the ossicles. These vibrations or sound waves, then travel into the cochlea. The ear canal is a tube running from the outer ear to the middle ear. It starts at the pinna, also known as the auricle, which is the outer portion of the ear. The ear canal then travels to the ear drum.
The ear drum is a thin membrane separating the external and the middle ear. It is here where sound is transmitted to the ossicles, small bones that transmit the sound to the cochlea. The cochlea is part of the labyrinth, or the inner ear. The labyrinth is fluid-filled passages containing the vestibule of the ear, the cochlea and the semicircular canals. It is responsible for hearing and balance.
Air conduction transmits sound to the coil-shaped cochlea. The fluid inside the cochlea moves in response to the vibrations. Cilia inside the cochlea then begin to move. This movement converts the vibrations into electrical signals. These electrical signals are then transported to thousands of nerve cells via neurotransmitters, or chemicals which pass on the nerve impulses.
Hearing tests can investigate how well a person hears. There is a hearing test to check air conduction and bone conduction hearing. The air conduction, or pure tone hearing test, uses headphones and a series of short of beeps at different intensities and intervals. The bone conduction test involves a bone oscillator, or vibrator, placed on the mastoid. The mastoid is a bone located behind the ear.
With air conduction hearing loss results from the bone conduction test are better. This difference is referred to as an air/bone gap. A hearing loss involving air conduction and bone conduction is called a mixed loss.
Air conduction hearing loss can be treated through the use of hearing aids. Hearing aids amplify sound. Cochlear implants are another hearing loss treatment option. These surgically implanted electrical devices, also referred to as a bionic ear, provide a sense of sound to individuals experiencing severe hearing difficulties or for those who are considered profoundly deaf.