How We Hear

By Diane Krieger Spivak

Joy of Hearing

Hearing, one of the five senses, helps us to be aware of the world around us and to communicate with others.

According to the American Hearing Research Foundation we hear sound when a series of sound waves, or vibrations, pass through the ear and reach our brain for interpretation.

Babies’ hearing is fully developed at birth, and science shows that they can hear even in the womb. According to the American Speech-Language-Hearing Association, the process of hearing involves the outer ear, middle ear and inner ear leading to the brain, enabling us to hear sounds ranging from extremely soft to extremely loud.

The outer ear includes the part that we see, on the outside of the head, as well as the ear canal and eardrum. Sound travels down the ear canal, striking the eardrum, causing it to vibrate.

The middle ear, behind the eardrum, contains the three smallest bones in the body, called ossicles. Formally called the malleus, incus, and stapes, they are commonly referred to by their shapes – the hammer, anvil, and stirrup. They are connected to the eardrum at one end and to an opening to the inner ear at the other end. When sound causes the eardrum to move, the ossicles also vibrate, causing the fluid in the snail-shaped inner ear, called the cochlea, to move, explains ASHA.

The inner ear is important in the transformation of the vibrations into electrical impulses, or signals, which are recognized by the brain. The movement of the fluid creates a back-and- forth motion of thousands of tiny hairs, called sensory receptors, lining the cochlea, says AHRF. The hair cells then send a signal along the auditory nerve, also called the hearing nerve, to the brain.

The brain then interprets these electrical signals as sound, says ASHA.

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