Hearing Testing

Normal hearing is essential for normal speech and language development in children. Even mild or fluctuating hearing loss can impact a child’s speech and language development. Though most children are now screened for hearing loss as newborns, it is important to retest hearing when there are concerns about hearing or speech/language development. Failure to meet the developmental milestones below should raise concern.

No child is too young to be tested for hearing loss. The earlier hearing loss is detected, the sooner the child can be helped to hear normally and to develop his or her best communication and social skills.

The most common methods used to test children’s hearing include:

• Audiogram
• Otoacoustic emission (OAE) testing
• Auditory brainstem response (ABR) testing or Brainstem Auditory Evoked Response (BAER) testing

Audiogram

Pure tone testing, represented by an audiogram, is the foundation of an audiological evaluation. Pure tone test results are used to confirm normal hearing or describe the configuration and severity of hearing loss. Most pure tone testing is performed in a sound-treated booth using headphones, through which tones are delivered. The patient is instructed to raise her or his hand or push a button when a tone is detected. With children or special-needs adults, play or visually-reinforced techniques can be used to assess responses to the tones. Screening using pure tone testing by audiometer should be conducted in a sound-treated booth or quiet area.

Pure tones are described in terms of their frequency (in cycles per second or Hz) and intensity (decibels or dB). They can be delivered through headphones, ear inserts, or a bone oscillator. Tones can also be presented through speakers but they require modification and are then referred to as frequency-modulated or FM tones. The most commonly evaluated frequency range is 250 Hz to 8000 Hz (low to high frequency), tested in whole octave steps (250, 500, 1000, 2000 etc.). Hearing threshold, measured in decibels (dB) for each frequency, is the softest level at which the person can hear the tone. For children who cannot be trained to listen for or clearly indicate the softest sound they can hear, minimal response level describes the softest sound to which the child appears to consistently respond – this level is most likely above threshold. An audiometer can also be used to test speech reception and recognition. Words are presented via a microphone and the patient is asked to repeat what he or she hears or the tester may observe a behavioral response (child turns to voice or points to body part when asked). This testing can indicate how softly and clearly the child can hear speech.

Thresholds or minimal response levels are documented on a graph called an audiogram. It shows how high the decibel level needs to be for a person to hear each frequency with each ear. If a person hears sound at 25 dB or less, hearing is considered normal.

The Human Hearing Chart to the left shows human hearing in hertz frequencies and the range that audiograms test. The range of hearing that the audiogram represents is shown on the chart in the shaded area labeled “AUDIOGRAM.” You can view a larger version of the Human Hearing Chart ( 1.0 MB). Image courtesy of Primary Children's Medical Center. Also, see an example of an Audiogram Showing Hearing Loss ( 269 KB).

Otoacoustic Emission (OAE)

Otoacoustic emission (OAE) testing is often used to test hearing in babies and small children and is the method most commonly used in newborn screening programs. The OAE involves placing a small probe in the baby’s ear that measures an active response, generated from the inner ear or cochlea, to clicks presented in the frequency range of about 800-4000 Hz. This test can only determine if normal cochlear function is present – it cannot specify the degree (mild, moderate, severe, or profound) or type (conductive or sensorineural) of hearing loss, if present. The range of hearing tested by OAE is shown on the human hearing chart in the shaded box labeled “OAE” (top near the middle). Many pediatricians and early intervention specialists use OAE to screen for hearing loss.

Auditory Brainstem Response (ABR) testing or Brainstem Auditory Evoked Response (BAER)

When conventional testing cannot be done, the ABR (aka Brainstem Auditory Evoked Response or BAER) is used. This is especially helpful with young children or older children with developmental delays that make behavioral testing unreliable. It can be performed on young infants during a natural sleep state. For older infants and toddlers, it is usually done with sedation because a child must be completely still during the test. ABR involves recording the brain’s activity in response to clicking sounds, in a frequency range from 500-4000 Hz, delivered to the child’s ear. The intensity of the sound can be increased up to about 105 dB. Compared with the broad range of human hearing, the frequency range of this test is somewhat narrow. However, the range that is tested encompasses the common frequencies that are needed for speech and language development. The ABR is not a hearing test but rather a test of the auditory-neural response to sound. ABR test reports may be complex but will include a summary that should include the clinical relevant findings and their implications for hearing and follow-up. See an example of a Child ABR Report ( 40 KB).

Hearing screening are often performed by para-professionals (MAs, CNAs) in a primary care office or other outpatient setting where there is oversight by a licensed medical provider. Diagnostic hearing testing should be performed by a licensed audiologist who is trained in testing children and has access to the various testing equipment needed to evaluate children. Children with special health care needs are best served by a pediatric audiologist trained in working with this population. Early Intervention programs will usually offer hearing testing, as will state programs focused on children with special health care needs and/or disabilities.

The cost of hearing testing can range from less than $100 for a screening evaluation to $100-$700 for a full diagnostic evaluation, depending on the comprehensiveness of testing. Sedated procedures will cost more because medical staff is needed to provide safe sedation with patient monitoring. In many cases insurance and other third party payers will cover the cost of testing. Co-pays and deductibles will apply, so each family should check their insurance benefits to understand the cost before testing is performed. Some insurance plans will require a referral from a physician.