The human ear
Small and very sophisticated, the human ear is composed of three parts: the external ear, the middle ear, and the internal ear.
The external ear includes the auricle and the auditory canal where cerumen, commonly called earwax, sometimes accumulates. The auricle collects the sound, modifies its resonance, and transmits it to the middle ear.
The middle ear is composed of a tympanic cavity where the ossicular chain comes together. The eardrum, extremely thin skin, is in some ways the entryway to the middle ear. It acts as a drum and is the first link in the ear's ossicular chain (composed of three small bones: the hammer, anvil, and stirrup).
The ossicular chain modifies sound impedance by travelling from a gaseous environment (air) to a fluid environment (perilymph/endolymph) in the internal ear. It must therefore be greatly amplified. The tympanic cavity gives way to the Eustachian tube whose function is to equilibrate air pressure from the middle ear.
The internal ear is the centre of hearing. Composed of a bony structure filled with liquid, it contains the cochlea (limacon), an organ shaped like a snail, as well as the vestibular system, which is responsible for balance. The cochlea transforms sounds into electrical signals that are then transmitted to the brain in order to decode the sounds perceived and allows us to understand them.