The ear is quite an amazing piece of engineering.
It is a complex organisation of bones, hairs, nerves and cells.
Sounds are picked up in the form of invisible waves and these are the funneled into the ear canal which then leads to the sound being processed and sent to the brain. This all happens in real time, so efficient is the organ.
The outer part of the ear (Pinna) channels sound travelling in the air into the ear canal. These sound waves then pass down the ear canal and hit the eardrum (Tympanic Membrane) which cause it to vibrate.
The eardrum is linked to three tiny bones (Ossicles) that are in turn attached to the cochlea (the main hearing organ), hence the vibrating eardrum causes a domino effect causing the tiny bones to move in a lever style action.
The cochlea is filled with fluid that moves as a result of the movement of the tiny bones. The movement of this fluid carries the vibrations to the tiny hair cells in the cochlea. These hair cells then play an active role in conveying this message to the nerve that is connected to the brain and turns it into a signal that we hear. All in a very small space of time that feels very instant.