To begin to learn how hearing and balance work a good introduction is an online overview from the American Speech-Language-Hearing Association. The overview begins:
Hearing is one of the five senses. It is a complex process of picking up sound and attaching meaning to it. The human ear is fully developed at birth and responds to sounds that are very faint as well as sounds that are very loud. Even in utero, infants respond to sound. The ability to hear is critical to the attachment of meaning to the world around us.
The ASHA webpage then explains the functions of the five sections of the hearing mechanism: 1. Outer ear, 2. Middle ear, 3. Inner ear, 4. Acoustic nerve, and 5. Brain’ s auditory processing centers.
Much more about hearing can be learned in the Open University’s Science and Nature materials about Hearing. The illustration with this learn node is from those Open University materials in the section about neural processing of auditory information. To get into even more minute details, the Proceedings of the National Academy of Sciences of the United States have an in-depth article on how visual speech speeds up the neural processing of auditory speech. Together these resources, and the links they in turn provide, are a starting learn node for many related hearing subjects.