It is important that all parents are aware of their child's hearing from the moment their child is born. Universal hearing screenings are performed in most hospitals around the country when a child is born. A clean bill of health at birth does not always indicate that your child will never have a hearing loss. A child's hearing can be affected by many things. Some children run a high risk of hearing loss due to heredity or perinatal complications including rubella, syphilis, low birthweight, meningitis, and asphyxia. Toddlers and preschool age children may acquire a temporary or permanent hearing loss with repeated middle ear infections. Older children may acquire a hearing loss with repeated exposure to loud noise such as loud music.
If you suspect your child has difficulty hearing, seek professional help immediately. Early intervention will help your child reach his or her full potential. A normal hearing child should:
Birth to 3 Months
- Startle or cry at loud noises
- Stop moving and seem to listen to speech or sounds
- Awaken at a loud sound
3 to 6 Months
- Look toward a sound or speaker
- Smile when spoken to
- Recognize mother's voice
- Enjoy rattles and other toys that make sounds
6 to 9 Months
- Respond to his or her name
- Babble and make lots of different sounds
- Respond to "no"
9 to 12 Months
- Turn or look when name is called
- Listen to people talking
- Respond to simple commands like "give me", "come here"
- Understand "bye-bye"
12 to 18 Months
- Point or look to objects or familiar people by name
- Imitate simple sounds or words
- Follow simple spoken directions
- Say 2-3 words by 12 months and 8-10 words by 18 months
How does the ear function?
In a normally functioning ear, sound waves travel from the environment to the outer ear, which is made up of the outer, visible part of your ear and the ear canal. The outer ear captures the sound vibration and sends it through the ear canal to the middle ear, causing the eardrum and three tiny bones (malleus, incus, and stapes) to vibrate. This vibration makes the fluid in the snail-shaped cochlea move, which stimulates thousands of tiny hair cells inside the cochlea. The hair cells change the mechanical vibrations into electrical nerve impulses while bending back and forth and sending these electrical signals to the hearing nerve. The hearing nerve then carries these signals to the brain, where they're interpreted.
People with sensorineural hearing loss or nerve deafness have hair cells which have been damaged or destroyed and cannot function. Hair cells can be damaged or destroyed through aging, heredity, disease, infection, or repeated or severe exposure to loud noise. If the hair cells don't work, the hearing nerve can't be stimulated and therefore can't send information to the brain. Thus, the person is unable to hear.
Hearing loss can be mild, moderate, or severe, depending on the number of hair cells that are defective, damaged, or destroyed. People with mild or moderate hearing loss may find that hearing aids, which simply make sounds louder, help. Those with profound or severe hearing loss might even have trouble understanding loud sounds. A hearing aid won't help in these cases, and a doctor might recommend a cochlear implant.