The outner ear (or pinna, the part you can see) serves to protect the tympanic membrane (eardrum), as well to collect and direct sound waves through the ear canal to the eardrum. About 1¼ inches long, the canal contains modified sweat glands that secrete cerumen, or earwax. Too much cerumen can block sound transmission. 

The middle ear, separated from the external ear by the eardrum, is an air-filled cavity (tympanic cavity) carved out of the temporal bone. It connects to the throat/nasopharynx via the Eustachian tube. This ear-throat connection makes the ear susceptible to infection (otitismedia). The eustachian tube functions to equalize air pressure on both sides of the eardrum. Normally the walls of the tube are collapsed. Swallowing and chewing actions open the tube to allow air in or out, as needed for equalization. Equalizing air pressure ensures that the eardrum vibrates maximally when struck by sound waves.

Adjoining the eardrum are three linked, movable bones called "ossicles," which convert the sound waves striking the eardrum into mechanical vibrations. The smallest bones in the human body, the ossicles are named for their shape. The hammer (malleus) joins the inside of the eardrum. The anvil (incus), the middle bone, connects to the hammer and to the stirrup (stapes). The base of the stirrup, the footplate, fills the oval window which leads to the inner ear.

The inner ear consists of a maze of fluid-filled tubes, running through the temporal bone of the skull. The bony tubes, the bony labyrinth, are filled with a fluid called perilymph.  Within this bony labyrinth is a second series of delicate cellular tubes, called the membranous labyrinth, filled with the fluid called endolymph. This membranous labyrinth contains the actual hearing cells, the hair cells of the organ of Corti. There are three major sections of the bony labyrinth: 

1. The front portion is the snail-shaped cochlea, which functions in hearing. 
2. The rear part, the semicircular canals, helps maintain balance. 
3. Interconnecting the cochlea and the semicircular canals is the vestibule, containing the sense organs responsible for balance, the utricle and saccule. 

First of all, we should know how we hear so that we understand what audiology and hearing loss are.

Outer ears catch a sound then transmit it into ear canal. The soundwave transmitting to tympanic membrane creates a vibration that makes ossicles move. The smallest ossicle (look like a hook) joints with the oval window between midle ear and inner ear. When the oval window vibrates, a liquid at the inner ear (ear-fluid) transmits impulses to the cochlea. These impulses transmit sounds to the brain. In this area impulses are turned into sounds that allow us to understand the meaning.