Sound is made up of tiny vibrations in the air. The process of hearing includes both the ear and the brain. The ear changes the sound vibrations into a signal that can be understood by the brain. The brain is the most important part of hearing since that is where sounds are converted into meaningful information. Any interruption or damage can cause hearing problems. The ear has three parts — the middle, inner and outer ear. Each part of the ear has a different job:
The outer portion of the ear (the pinna) is cupped so that it can capture the sound vibrations in the air. These vibrations travel through the outer ear canal and collide with the eardrum. This causes the eardrum to vibrate. Cerumen, or earwax, can disrupt this sector and cause varying levels of hearing impairment.
The vibration of the eardrum moves the three small bones (called ossicles) in the middle ear. Common names for the bones are the hammer, anvil, and stirrup. They are also known as the malleus, incus, and stapes. These bones amplify the vibration and transfer the sound waves to the inner ear (the cochlea). This is where the ear drum resides. Often, hearing loss occurs in the middle ear.
The cochlea is a small snail-shaped organ in the temporal bone. It is divided into three channels, each filled with fluid. The vibrations from the ossicles are absorbed into the fluid-filled channels like waves in a pond. The middle channel contains the organ of Corti and sensory hair cells. Movement of the fluid starts a chain reaction that causes these hair cells to bend. Bending of the hair cells sends electrochemical impulses to the cochlear nerve (CNVIII) which carries the signal to the brain. Sensorineural hearing loss occurs here when the tiny hair cells suffer damage.
The auditory cortex in the brain interprets the electrochemical impulses into a meaningful message. We interpret the message according to our experiences in life. Audiology is centered on this concept.
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