Parents who have just received word that their child is deaf or hard of hearing can display a wide range of reactions. Most parents wonder what caused their child's hearing loss. The first step in understanding hearing loss is to understand how we hear and the types of hearing loss.
How the Ear Works
How We Hear
Sounds are all around us.
We hear when these sounds pass through the outer, middle and inner parts of our ears, sending thousands of tiny vibrations up to our brain for interpretation.
First sound travels through the outer ear canal and makes the eardrum move. When the eardrum moves, the three middle ear bones vibrate. This vibration creates movement of fluid in the inner ear also known as the cochlea.
The fluid movement causes sensory receptors in the coiled shaped cochlea, to send a signal along the auditory nerve to the brain—and this is how we hear.
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Outer Ear: Sound waves travel through the ear canal and makes the eardrum move.
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Middle Ear: When the eardrum moves, the ossicles (middle ear bones) vibrate. This vibration creates movement of fluid in the inner ear.
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Inner Ear: The movement of fluid causes the inner ear to send nerve signals to the brain. Once the brain receives the message, it identifies that message as sound
Types of Hearing Loss
Hearing loss may be located in the outer, middle and/or inner ear. There are 3 types of hearing loss:
Conductive Hearing Loss
Conductive hearing loss is caused by a problem in the outer or middle ear resulting in sound being unable to travel to the inner ear properly. Many instances of conductive hearing loss can be treated with medicine or surgery. Causes of conductive hearing loss can include wax in the ear canal, fluid in the middle ear or a hole in the eardrum.
Sensorineural Hearing Loss
Sensorineural hearing loss is caused by a problem in the inner ear. Sensorineural hearing loss usually cannot be cured with medicine or surgery, but hearing aids or cochlear implants can help in most cases. In young children, sensorineural hearing loss can occur due to:
- Certain infections before birth
- Lack of oxygen during birth
- Genetic causes
Mixed Hearing Loss
Mixed hearing loss is a combination of conductive and sensorineural hearing loss. An example of mixed hearing loss is when children with sensorineural hearing loss also have middle ear problems (such as fluid in the middle ear). This can make hearing loss worse.
Determining the Type of Hearing Loss
Air Conduction Test
During a hearing test, sounds are presented in different ways. Air conduction testing looks at how the whole hearing system responds to sound. When testing with earphones or loudspeakers, the sounds go into the ear canal, through the middle ear to reach the inner ear. This is known as
air conduction testing.
Bone Conduction Test
If air conduction testing shows a hearing loss, another device called a bone vibrator is placed behind the ear to send sounds directly to the inner ear. Sounds are sent through the bones of the head and do not pass through the eardrum or the middle ear. This is called
bone conduction testing.
