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 in to a signal that can be understood by the brain. Any interruption along the auditory pathway from the outer ear to the brain can cause hearing problems. The ear has three parts—the outer, middle and inner 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). Often, hearing loss occurs in the middle ear. Hearing loss caused by problems in the idle ear is often reversible.
The cochlea is a small snail-shaped organ in the temporal bone. It is divided in to three channels, each filled with fluid. The vibrations from the ossicles are absorbed in to 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 in to a meaningful message. We interpret the message according to our experiences in life. Auditory processing in the brain can be affected by auditory deprivation, hearing loss, aging, strokes or concussions.
Video | with Alison
Listen to our Audiologist Alison Burton talk about the Ontario Infant Hearing Program.