There are a variety of tests that can be used to find out how much hearing your child has.
Why are there different tests?
The tests used will depend on your child’s age and stage of development. It’s possible to test the hearing of all children from birth. Screening tests are normally done first and if it’s likely that there’s a hearing loss, the child will be referred to an audiologist. The audiologist will then perform a range of objective and/or behavioural tests to build up an accurate picture of your child’s hearing.
Objective hearing assessments
These use test techniques that measure the function of the ear or hearing nerve pathways. They don’t require a response from the child to show that they’ve heard the sound. There are two types of objective hearing assessments.
The OAE test is an objective hearing test that works on the principle that a healthy cochlea (inner ear) will give a faint response when stimulated with sound. The cochlea contains outer hair cells which produce this response to sound. The OAE test gives information about how well the outer hair cells are working.
This is the test that is part of the newborn hearing screening, but can be carried out on older children as well.
How does the test work?
A small ear piece, containing a speaker and a microphone, is placed in the child’s ear. A clicking sound is played and if the cochlea is working properly the microphone in the ear piece will pick up the response.
This is recorded on a computer that tells the person carrying out the test if a response is present or not. When a baby has a clear response during their newborn hearing screening then they won’t need any more tests.
Although it's a test of how the ear is working, the OAE test can't give information about levels of hearing loss. The screening test is very quick and gives the result straightaway.
What does the result mean?
A poor response to an OAE test doesn't necessarily mean that a child is deaf. It can be difficult to get a response if a child is unsettled at the time of the test, if the room is noisy or if there's any fluid in the ear.
In babies this test is usually repeated before referral for the second type of screening test, which is called auditory brainstem response (ABR).
This objective hearing test is usually done following a newborn hearing screening, but can be carried out on older children as well.
What is the ABR test?
The ABR measures whether sound is being sent from the cochlea (inner ear) and through the auditory (hearing) nerve to the brain. It is used as a screening test as part of the newborn hearing screen (automated auditory brainstem response – AABR – where the computer judges if there’s a response at quiet levels of sound).
Following newborn hearing screening a more detailed test can be carried out where different levels of sound are used and the audiologist interprets the results to find the quietest level of sound being picked up by the hearing nerves.
How does the ABR test work?
The audiologist will place three small sensors and a set of headphones on the child’s head. For an accurate result, the child must be very still and quiet throughout the test. In young babies the test can be carried out while they are sleeping. In slightly older children, a light sedative or an anaesthetic may be offered.
How is the result used?
In very young children or children who aren’t developed enough to have behavioural hearing tests, the results of the ABR test can be used to accurately fit hearing aids if they are needed. In older children this test may be used to confirm the results of their behavioural test.
Behavioural hearing assessments
These use test techniques where the audiologist records the child’s response to sound. This might be a startle, look or head turn in a baby, or an older child moving a toy or saying “yes” when they hear a sound.
As a child develops, their audiologist will assess their hearing using behavioural tests. These tests use toys and play as part of the assessment and involve your child listening for different sounds as part of a game.
There are three types of behavioural hearing assessments.
Visual response audiometry (VRA)
Visual response audiometry is suitable for children from six months to about two-and-a-half years. Using a machine called an audiometer, sounds of different frequencies and loudness are played through speakers. When the child hears the sound, they will turn their head and a visual ‘reward’ is activated, such as a toy lighting up or a puppet.
The test can check the full range of hearing but doesn’t give specific information about each ear. If your audiologist feels it’s important to get information about each ear individually, this test can be done with small earphones placed in your child’s ears.
From about the age of three, children are actively involved in testing by using a technique called conditioning. Younger children are shown how to move a toy (for example, putting a peg into a board) each time they hear a sound.
Older children are asked to respond to sounds by saying yes or pressing a button. The sounds come through headphones, earphones placed inside the child’s ear, or sometimes through a speaker (when the test is known as soundfield audiometry).
Otoacoustic emissions (OAE) tests, auditory brainstem response (ABR) tests, VRA and pure tone audiometry all use air conduction (sounds passing through the ear canal and middle ear before reaching the cochlea) to test hearing.
ABR, VRA and pure tone audiometry can also be tested using bone conduction.
Bone-conduction testing is performed in a similar way to air-conduction testing. A small vibrating device is placed behind the child’s ear. This allows sound vibrations to pass directly to the inner ear through the bones in the head bypassing the outer and middle ear. This technique is useful for identifying whether a hearing loss is conductive or sensorineural.
Speech discrimination tests
Speech discrimination tests check the child’s ability to hear words at different listening levels. The tester asks the child to identify toys or pictures, or to copy words spoken by themselves or from a recording. From this the tester can assess the quietest level at which the child can correctly identify the words used. This test can also be used to assess lip-reading and signing skills.
Tympanometry isn’t a test of hearing; it’s used to check how well the moving parts of the middle ear are working. Your child will have this test as part of their hearing assessment.
A small earpiece is held gently in the ear canal. A pump causes the pressure of the air in the ear canal to change. The eardrum should move freely in and out with the change in pressure. The earpiece measures this by checking the sound reflected by the eardrum. If the eardrum isn’t moving freely, there’s likely to be some fluid or another problem with the middle ear. This build-up of fluid is usually caused by glue ear.
Questions to ask at your child’s audiology appointments
As a parent, it’s important that you understand the hearing tests that are being carried out on your child and what the results mean. Below is a list of some questions you may wish to ask at your child’s audiology or ear, nose and throat (ENT) appointments.
- Do you have a copy of the most recent hearing test and the referral letter?
- What tests have been carried out? Will there be a need for further testing?
- What type of hearing loss does my child have (sensorineural, conductive, or mixed)? Please explain what this means.
- Will my child need to be referred to another health professional? For example, an eye doctor or a geneticist?
- Do you think our family should have genetic counselling?
- Does my child need other tests? E.g. scans (CT, MRI), heart (ECG), blood, urine tests or eye tests. What will these tests tell you about my child’s hearing loss?
- Will my child’s hearing loss improve or get worse?
- What caused my child’s hearing loss?
- Do we and other members of our family need to have our hearing tested?
- What options are available for my child? (e.g. grommets, hearing aids or cochlear implants).
- Will a hearing aid help my child to hear?
- When will my child be fitted with hearing aids?
- Is a cochlear implant an option for my child? Where can I get more information?
- Will the hearing loss affect my child’s development?
- Will my child be able to hear me?
- How often will my child return for follow-up appointments?
- Can you explain my child’s audiogram to me?
- Is there any local support for deaf children and their families?
- Can you refer me to other support services such as a Teacher of the Deaf, speech and language therapy or a social worker for the deaf?