How We Hear

The Outer Ear

The pinna is the outer visible portion of the ear. It collects the sound and funnels it into the ear canal. The ear canal is ‘S’ shaped and is such that frequencies get amplified by its structure. The ear canal contains wax secreting glands and hair follicles, both form the protective structures of the ear.

The sound then reaches the ear drum and causes it to vibrate. The ear drum is an oval shaped flexible membrane.

The Middle Ear

The middle ear is an air-filled cavity which has the 3 tinniest bones of the human body viz. malleus, incus and stapes. The Malleus is attached to the ear drum on one side and to the incus on the other, the incus is then attached to the stapes, and the stapes is attached to the oval window. Thus, the middle ear bones conduct and amplify the sound received by the ear drum to the inner ear i.e. the cochlea.

The Eustachian tube is a narrow tube which is responsible to maintain the air pressure within the middle ear and the outside air. This tube descends from the floor of the middle ear and opens in the neck.

The Inner Ear

The inner ear consists of two structures, the snail shaped organ i.e. the cochlea which is fluid filled and the vestibular organ which is responsible for balance.

Through the oval window, the sound enters the cochlea and displaces the fluid inside it. As this fluid moves, the corresponding frequency nerve endings are set into motion. These nerve endings transform the vibrations into electrical impulses which then travel along the auditory nerve to the brain.

The ear does the function of conduction of sound to the brain, the brain does the interpretation of this sound energy.