The ear consists of three parts: the outer, middle and inner ear. The outer ear collects the sound waves and conducts them to the middle ear. There, the middle ear amplifies the sound and transmits it to the inner ear. The inner ear converts sound vibrations into electrical impulses that travel through the auditory nerve to the brain.

The outer ear collects the sound waves and leads them to the auditory canal.
The ear canal carries the sound waves to the eardrum (tympanic membrane) which cause vibrations in it.
The bones in the middle ear (hammer, anvil and stirrup) detect and transmit these vibrations.
The vibrations pass through the oval window into the cochlear, setting the cochlear fluid in motion. This causes the sound waves to be transformed into electrical impulses by the special nerve cells.
The auditory nerve carries these electrical impulses to the brain, where they are recognized by the hearing center.