It is never too early to test a child's hearing. The type of procedure used to test hearing will depend upon the age of the child.
Common Types of Testing
Soundfield (Behavioral) Testing
During soundfield testing, the child sits on the parent's lap. Sounds are presented to the soundfield via loudspeakers. The audiologist(s) watches the child as he responds to the sounds. In very young children, the audiologist will look for responses such as an eyeblink or slight body movement. Older children are trained to turn toward the sound. When turning toward the sound, the child then will see a lighted toy as a reward.
Testing Under Headphones
Headphone testing provides the audiologist with information regarding the child's ability to hear with each ear. Testing usually begins by finding the softest level at which the child is able to repeat words or point to pictures. The child then is taught to respond to the sounds of various pitches by raising his hand or by performing an act such as dropping a block into a container. This test is referred to as an audiogram and evaluates the child's ability to hear certain sound frequencies.
Bone Conduction Testing
Bone conduction testing evaluates the function of the inner ear or nerve portion of the ear. A small vibrator is placed behind the child's ear and he is asked to repeat or identify words or respond to sounds of different frequencies. The results of this test are compared to results obtained under headphones or through loudspeakers to help the audiologist identify the type of hearing loss.
Otoacoustic Emissions
Otoacoustic emission testing assesses the function of the inner ear, specifically the outer hair cells. A small probe is placed in the child's ear. Sounds are presented to the ear and an emission ("echo") from the ear is measured. The result helps us to determine whether a child has normal hearing.
Immittance Testing
Immittance testing, often referred to as a tympanometry, provides information regarding eardrum mobility and middle ear function. A small plastic tip is placed in the child's ear to make an airtight seal. Changes in air pressure are made and measures are taken. If the child has ear tubes, this test helps determine if the tubes are in place, open, and working properly. If the child does not have tubes, this test helps determine if there are any signs of fluid or other problems in the middle ear. Reflex action of the ear (acoustic reflexes) also is measured with immittance testing.
Auditory Brainstem Response (ABR) Testing
The ABR is a test that provides information regarding the softest level of sound that a person can hear. During the test, several electrodes are taped onto the child's head and a small earphone is placed into each ear. These electrodes are used to monitor brainwave activity as the child listens to sounds at different levels of loudness.
The brainwave patterns of the ABR are evaluated to determine the softest level of sound each ear can hear. If there is a hearing loss, the ABR helps to determine the type and severity of the problem.
Who Should Have an ABR?
The ABR is most commonly recommended for infants or very young children when a hearing loss is suspected. It can also be used to evaluate older children who will not cooperate during other types of hearing tests. The ABR is usually not necessary in healthy children over three years of age, if the child will wear headphones and cooperate during a behavioral hearing test.
The ABR often is performed as part of a complete test battery, which includes behavioral testing and tympanometry and otoacoustic emissions. It is important that a series of tests be performed to more accurately determine the presence, degree and type of hearing loss.