Hearing is possible through auditory organ. But the inner ear also accommodate the sensory orgain for the balance of the sense. Both constitue of one unit. The outer ear, middle ear and cochlea of the inner ear constitute the organ for perceiving sound.

The outer ear includes the auricle (concha auriculae) and the external auditory canal (meatus acusticus externs) together the eardrum (membrana tympani) as boundary between the outer ear and middle ear (cavum tympani).
The middle ear is also called the tympanic cavity (cavum tympani), which is continued in the Eustachian tube (tuba auditiva) as connection to the upper part of the throat.

The inner ear has a highly complex system of passages and cavities called the bony labyrinth. It is filled with a liquid, the perilymph. In this liquid there is a membranous labyrinth similarly filled with liquid (endolymph). This is the organ for auditory sensation but also the organ of balance (vestibular system).
The hearing organ is a particularly important sensory organ since, apart from the ability to hear, it is a prerequisite for developing speech. This is why it is more important than the eye.