How Hearing Works:
Hearing is one of the five senses. It is a complex process of detecting sound and attaching meaning to it. The ability to hear is critical to understanding the world around us.
The human ear is fully developed at birth and can respond to sounds that are very faint as well as sounds that are very loud.
The ear can be divided into three parts leading up to the brain – the outer ear, middle ear and the inner ear.
- The outer ear consists of the pinna and the ear canal. The pinna – the part of the “ear” that we see on each side of our head, serves as a collector of sound vibrations around us and guides the vibrations into the ear canal. The lumps and ridges in the pinna help us decide the direction and source of sound.
- The middle ear begins with the eardrum at the end of the ear canal and also includes the air filled space behind the ear drum. The middle ear space contains three tiny bones, called the ossicles. These three bones form a connection from the eardrum to the inner ear. As sound waves hit the eardrum, the eardrum moves back and forth causing the ossicles to also move. As a result, the sound wave is changed to a mechanical vibration.
- The inner ear contains the sensory organs for hearing (the cochlea) and balance (the semi-circular canals). The cochlea is a bony structure that is filled with fluid and contains sensory hair hells, the nerve receptors for hearing. The mechanical vibration passed on from the middle ear system moved a membrane in the cochlea known as the oval widow which in turn passes the vibration on to the fluid within the cochlea. The vibration of the fluid then bends and stimulates the sensory hair cells. The hair cells then change the vibration of the fluid into nerve impulses which are then passed up the hearing nerve to the auditory cortex in the brain.