The ear has three main parts: outer, middle and inner.
The outer ear (the part you can see) opens into the ear canal. The eardrum separates the ear canal from the middle ear. Small bones in the middle ear help transfer sound to the inner ear. The inner ear contains several channels of fluid and specialized cells that detect fluid motion. These cells are connected to the auditory (hearing) nerve, which leads to the brain.
Any source of sound sends vibrations or sound waves into the air. These funnel through the ear opening, down the ear, canal, and strike your eardrum, causing it to vibrate. The vibrations are passed to the small bones of the middle ear, which transmit them to the fluid of the inner ear. Here, the fluid vibrations become nerve impulses and go directly to the brain, which interprets the impulses as sound (music, voice, a car horn).
If a problem arises in the outer or middle portion of the ear, a conductive (or mechanical) hearing loss (CHL) is present. Common causes of CHL are fluid in the middle ear from ear infections or an ear plug. If the inner ear or hearing nerve is damaged, a sensorineural hearing loss (SNHL) develops. The common forms of SNHL are from genetic (hereditary) factors or infections (i.e., meningitis). In general, CHL can be corrected with medicine or surgery, while SNHL is usually not reversible.