Hearing tests are used to diagnose problems in a child’s ability to hear sounds. These tests are frequently performed shortly after an infant’s birth, and again before the child starts school. Children who are at higher risk for a hearing loss may be tested periodically, as such problems sometimes take time to develop.

The process of hearing begins when the outer ear detects sounds from the environment and ends when a portion of the inner ear called the cochlea turns vibrations into electric signals that are sent to the brain. When something interferes with this ability to process sound, a hearing loss may result.

Proper hearing is crucial to developing normal speech and language abilities. For this reason, experts emphasize the importance of diagnosing a hearing impairment within the first six months of a child’s life. Today, many states have laws requiring that a baby’s hearing be tested following birth and before the child leaves the hospital.

There are two major types of hearing tests. Electrophysiologic tests measure a child’s ability to hear based on electrical information generated from the auditory nervous system. Behavioral tests use a technique called audiometry – in which tones are introduced to a child in a soundproof room – while an expert in hearing (audiologist) observes the child’s responses to these sounds.

In addition to these tests, tympanometry sometimes is performed to measure the eardrum’s response to soft sounds or air pressure in the ear canal.

Most hearing tests are performed in a hospital or other facility with a soundproof room. These tests unfold differently depending on the nature of the test being performed. Once a hearing deficiency has been diagnosed, early treatment is crucial to long-term prognosis. Children who are treated by the age of 6 months usually develop language skills that are similar to the level of their peers.

Some hearing problems are temporary and will disappear as soon as an underlying condition is treated. For example, using antibiotics or undergoing surgery can help clear an ear infection, which in turn should eliminate any associated hearing loss.

However, other forms of hearing loss are permanent. Hearing aids are commonly used to treat such hearing problems. These instruments consist of a microphone, amplifier and receiver that work together to boost a child’s ability to hear. Other hearing devices that may help include an FM system and a cochlear implant. Some children with hearing loss may benefit from learning to lip-read or from listening therapy.

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.

Even mild hearing loss can significantly impact a child’s ability to develop normal speech and language abilities. For this reason, children’s hearing should be tested at a young age. In many states, it is required that babies have their hearing tested before they leave the hospital following birth.

The Centers for Disease Control and Prevention (CDC) recommends that babies have their hearing screened before they leave the hospital following birth, or before 1 month of age. Babies who do not pass this test should receive a follow-up screening at 3 months of age. If a baby is found to have a hearing impairment, treatment and other services should begin by the time he or she is 6 months old.

The CDC also recommends that children have their hearing tested again before beginning school, as some forms of hearing loss develop over time.

There are several types of hearing tests. Newborns are likely to undergo one of three types of electrophysiologic tests, which measure a child’s ability to hear based on electrical information generated from the auditory nervous system. These tests include:

• Auditory brainstem response (ABR). This test measures the function of a child’s brainstem in reaction to sound and can reveal information about hearing sensitivity and the brainstem’s response to sound. While a child is asleep, small earphones are inserted into the ear canals. Electrodes to measure the brainstem response are placed on the baby’s head. These devices do not harm the child. A series of clicking sounds are introduced through the earphones, and the electrodes record the hearing nerve’s responses to these sounds. These measurements are shown on a computer as a waveform and a pass-fail verdict is automatically generated – interpretation of the data by an audiologist is not required. An abnormal result may indicate hearing loss or another medical problem. In some cases, difficulties with the measurement process can cause a false abnormal result.
  
  
• Auditory steady state response (ASSR). Often performed with the ABR. The sound is transmitted into the ear and a computer detects brain waves in the hearing section of the brain. The computer then measures the child’s hearing capacity.
  
  
• Otoacoustic emissions (OAE). Performed on sleeping newborns in a hospital or older children who are able to sit quietly. A tiny, flexible sponge microphone/probe is placed in the ear canal and a series of pulse sounds are introduced. The echo generated from the inner ear in response to these sounds is recorded and averaged by a computer. If no echo is measured, a hearing loss may be indicated. In some cases, an ear infection may prevent an echo from being measured even if the child’s hearing is normal. Children who fail an OAE test often will take an ABR to confirm hearing loss.

While these tests help measure the structural completeness of the auditory pathway – and thus the child’s ability to detect sound – they do not actually measure the child’s hearing. Instead, behavioral tests are used for this purpose. In these tests, an audiologist uses a technique called audiometry, in which tones are introduced to a child in a soundproof room, usually via headphones. The audiologist observes the child’s responses to these sounds. Audiologists are trained to notice a child’s bodily reactions to sound, such as changes in body movement, opening or widening of the eyes, and changes in the child’s sucking rate. Behavioral tests can measure hearing thresholds at specific frequencies and reveal the degree of hearing impairment, if any, a child is experiencing.

Examples of these behavioral tests include:

• Visual reinforcement audiometry. The child sits on the parent’s lap in the middle of a soundproof room with speakers. When a tone is introduced, the child is supposed to turn toward the sound. Estimates are then made of the child’s sensitivity to tones and speech sounds. This test is typically used in children between the ages of 6 months and 30 months.
  
  
• Play audiometry. Also known as conditioned play audiometry (CPA), it involves training children to use play to respond to sounds they hear by performing a certain action. For example, a child may be asked to put a piece into a puzzle, drop a block into a bucket or put a ring on a peg whenever a particular sound is heard. This test typically is performed between the ages of 2.5 and 4 years.
  
  
• Standard audiometry. Also known as pure tone audiometry. When a tone is introduced, the child presses a button or raises a right or left hand depending on which ear hears the sound. This is the standard method of hearing testing used for children who are age 4 and older, as well as for adults.

In addition to these tests, tympanometry sometimes is performed to measure the eardrum’s response to soft sounds or air pressure in the ear canal. A tympanometry cannot in itself reveal whether a child can hear. But it can be used to identify physical problems such as collected fluid behind the eardrum. The information gathered in this test is represented on a graph known as a tympanogram. A flat line indicates that the eardrum is not responding properly.

In addition, a new auditory testing tool that measures whether a child’s nervous system is able to accurately translate sounds into brain waves is now available for professional use. The BioMAP is a user-friendly device that uses noninvasive electrodes placed on a child’s scalp and an earpiece that delivers carefully calibrated sounds in one ear. As the child watches a movie or video, the tester is able to measure the brain’s response to the sounds. Testing with BioMAP is relatively easy, painless and takes about 20 to 30 minutes to complete. The BioMAP device can help identify when a child has sound encoding problems related to learning disorders. These differ from hearing problems and would not be distinguished by standard hearing tests. Specialists (e.g., speech therapist) can then provide the child with auditory training that can improve their ability to distinguish sounds.

Parents should consult with their physician about any preparatory steps their child needs to take prior to the hearing test. Usually, these will be minimal. Prior to the test, a physician may perform a complete physical examination and compile a thorough medical history to evaluate potential causes of a child’s hearing problem.

Most hearing tests are performed in a hospital or other facility with a soundproof room. These tests unfold differently depending on the nature of the test being performed. A pediatric audiologist usually performs any behavioral tests. This is a specialist who can evaluate a child’s hearing loss.

It is important to note that a failure to pass an initial hearing test does not necessarily mean that a child has hearing loss. This is a commonplace occurrence, and follow-up testing is necessary to make sure that the child’s hearing is in fact deficient.

If a hearing loss is confirmed, the child likely will be referred to experts such as a hearing expert (known as an audiologist) and a pediatric ear, nose and throat specialist (known as an otolaryngologist). These experts can work together to further pinpoint the nature and source of a child’s hearing loss and to formulate a treatment plan.

In some cases, a child’s hearing loss may be caused by a condition such as an ear infection. Such hearing loss is temporary, and usually clears once the underlying condition is effectively treated with techniques such as medication therapy or surgery.

However, some forms of hearing loss are permanent. Early treatment of such hearing problems is crucial to long-term prognosis. Children who are treated by the age of 6 months usually develop language skills that are up to the level of their peers.

In many cases, a child with a hearing deficiency may require a hearing aid. This is an instrument that consists of a microphone, amplifier and receiver. Hearing aids are available in various styles. Some are placed in or behind the ear, while others are worn on the body. If the hearing loss affects both ears, two hearing aids likely will be suggested.

The major drawback of hearing aids is expense. They can cost several hundred dollars each, and this cost often is not covered by insurance. Families who cannot afford such costs may be eligible for government aid that can help with the expense of hearing aids.

Some children benefit from a specialized amplification device known as an FM system. This instrument helps a child to hear well in a noisy environment (e.g., school). Other children may benefit from learning to lip-read or from listening therapy or other types of auditory training.  

Children who have profound hearing loss that cannot be helped by hearing aids may benefit from a cochlear implant. This helps transmit sound past the damaged cochlea directly to the nerve of hearing.

Preparing questions in advance can help patients and parents have more meaningful discussions with physicians regarding their or their child’s treatment options. The following questions related to hearing tests may be helpful:

1. Will my physician tell me if my child’s hearing was tested in the hospital after birth?
   
   
2. If my child’s hearing was not tested after birth, how soon should it be tested?
   
   
3. How will I know if my child is in an “at-risk” group that requires regular testing of hearing?
   
   
4. What signs should I look for that might indicate that my child has a hearing problem?
   
   
5. What tests will you use to diagnose the nature of my child’s hearing problem?
   
   
6. How long will testing take?
   
   
7. How should my child prepare for the test?
   
   
8. Is my child’s hearing loss permanent or temporary?
   
   
9. What are my child’s treatment options?
   
   
10. What are the pros and cons of each option?
    
    
11. How often should I have my child’s hearing tested?