Hearing tests help physicians to detect deficiencies in a child’s ability to hear sounds. Proper hearing is important for developing normal speech and language abilities. For this reason, experts emphasize the importance of diagnosing and treating a hearing impairment before a child is over 6 months old.

The process of hearing begins when sounds from the environment are funneled into the outer ear. The sound travels through the eardrum (the tympanic membrane that vibrates in response to sound waves) and into the middle ear. There, three small bones (ossicles) – known as the hammer, anvil and stirrup bones – begin to vibrate, sending the sound signals to the inner ear. In a portion of the inner ear called the cochlea, the vibrations are turned into electric signals that move along the auditory nerves on their way to the brain.

Infants who have normal hearing usually are startled by a loud noise and may jump in reaction. As infants grow, hearing becomes more precise. By three months of age, most infants can recognize a parent’s voice and by six months, infants are able to turn their heads toward the source of a sound. By the time children are 1 year old, they can imitate some sounds they hear and form their own simple words.

When something interferes with a child’s ability to process sound, a hearing loss may result. Problems with hearing are among the most common major abnormalities in babies, according to the American Academy of Pediatrics (AAP). Hearing loss in both ears is present in between one and three infants out of every 1,000 who are born healthy, and in between two and four infants out of every 100 who need intensive care following birth. In some cases, a hearing loss does not develop until later in a child’s life.

There are four major types of hearing loss:

• Conductive hearing loss. Occurs when something interferes with the process of sound transmission to the inner ear. Ear infections (otitis media) are a major source of conductive hearing loss. In most case, this type of hearing loss is mild and disappears when the underlying condition is treated with medication or surgery.
  
  
• Sensorineural hearing loss. Occurs when a malformation, dysfunction or damage to the cochlea or auditory (hearing) nerves causes hearing loss. It typically is present at birth and may be the result of genetics or due to a medical problem. The degree of hearing loss can range from mild to profound. It may be evident in just one ear or in both ears, and may get progressively worse over time. In most cases, children with sensorineural hearing loss will not regain their hearing. However, hearing aids can help children with this type of loss to hear more clearly.
  
  
• Mixed hearing loss. Occurs when hearing loss is a result of both conductive and sensorineural factors.
  
  
• Central hearing loss. Occurs when hearing loss involves the areas of the brain used to hear. Children with this condition have brains that struggle to process speech and other auditory signals.

The AAP and other organizations have stressed the need to screen the hearing of newborns. Relying solely on physicians and parents to recognize signs of hearing loss has not proved sufficiently effective in the past, according to the AAP. As a result, the average age of detection of significant hearing loss is 14 months. Experts generally stress the importance of detecting hearing problems before a child is 6 months of age. 

Hearing tests typically are recommended for all newborn children. These tests should be repeated in any child who shows symptoms indicating a hearing problem. Such signs include not speaking clearly after age 1, not reacting to loud noises, inattentiveness and learning difficulties. Children who fail to respond when spoken to or who constantly increase the volume on the television also may have hearing problems. The AAP also recommends hearing tests at ages 4, 12, 15 and 18 years.

Regular testing also may be recommended for children who are at high risk of having a hearing deficiency. This includes children who were born prematurely, spent time in a neonatal intensive care unit, have taken medications associated with hearing loss, have a family history of childhood hearing loss or had complications at birth (e.g., skull or facial deformities). A history of ear infections and other types of infections (such as meningitis or cytomegalovirus) also are risk factors for hearing loss. 

In addition to formal testing, parents can play a crucial role in helping reveal their child’s hearing loss. Studies show that a parent’s day-to-day observation of a child is often a more effective tool for detecting hearing deficiencies than a single physician’s examination. 

Parents can informally test their child’s hearing by using techniques such as standing behind their baby and clapping to see if the child reacts, standing behind the baby and calling to see if the child looks around (babies younger than 6 months may have trouble locating the source of the sound) or simply keeping track of the child’s everyday responses to sounds.