What happens to the sound waves once they reach the ear?



What happens to the sound waves once they reach the ear? How do various structures of the ear transform sound waves so that the brain can understand them? The answers to these questions can be obtained by studying the structures and functions of the human ear. The ear has three major structures: the outer ear, the middle ear, and the inner ear.

Outer Ear:

It is the external or outer part of the ear which can be seen from outside. It is made up of the pinna and the auditory canal. The pinna is the 9 external part of the ear, which can be seen from outside. Sound waves arriving at the pinna are funneled into the auditory canal, which is a tube like passage leading to the eardrum. The auditory canal connects the outer ear with the middle ear, which is a structure often filled with wax.

Middle ear:

It contains the eardrum (the tympanic membrane), and three small bones. The three small bones are the hammer; the anvil, and the stirrup. The bones are so named because of their structures. The eardrum works like a miniature drum, which vibrates when the sound wave hit it. The more intense the sound waves, the more the vibration are the erdrum. The sound waves then touch the three bony structures, which also vibrate and conduct the sound waves. The middle ear acts like an amplifier making us aware of sounds that would otherwise go unnoticed. The three bones have one important function to transmit vibrations to the oval window, a thin membrane leading to the inner ear. The oval window, which is attached to stirrup, balances air pressure in the middle ear. Hence, the main function of middle ear is to give a mechanical framework to sound waves.

Inner Ear:

The important structures of inner ear are the cochlea, the basilar membrane, and the organ of corti. The inner ear is a portion of the ear that changes sound waves into a form that allows them to be transmitted to the brain. The cochlea has the shape of a snail shell. The cochlea has three fluid-filled canals spiraling around together and separated from one another by membranes. The three canals are vestibular canal, the cochlear canal, and the tympanic canal. One of the membranes lies coiled within the cochlea and is called the basilar membrane. Vibrations in the fluids within the canals of the inner ear strike against the basilar membrane. The waves in the canals reach the organ of corti, which is attached to basilar membrane. The organ of corti has thousands of hair-like structures, which are the real auditory receptor cells. The pressure waves in the cochlear canals produce bending movements of the fine, hair like processes on the ends of the hair cells of the organ of corti. The bending of these receptor cells generates a neural impulse that is transmitted by the auditory nerves to the auditory cortex of the temporal lobes in the brain. Then we hear the message.