Hearing tests and your child
Audiologists use many different hearing tests. The ones they use will depend on the age of your child, what they are trying to find out, and the nature of their deafness. We will now explain the different types of hearing tests used and the terms you might hear. We have kept all of this information on one page so it is easier for you to refer back to whenever you need.
Different hearing tests
Audiologists use different tests to check different parts of the ear and different stages in the process of hearing. Building up a detailed picture of your child’s deafness will therefore take time as you and your audiological team put together each piece of the jigsaw. Different hearing tests also enable us to answer questions such as:
- Is my child’s hearing as it should be?
- Can my child’s deafness be treated or is it permanent?
- What sounds can my child hear?
- How will my child’s deafness affect his or her ability to speak?
- What can be done to help my child hear more?
We will now take a look at the range of hearing tests covering from birth to primary school.
- Objective measures
- Behavioural tests
- Speech tests
- Air and bone conduction
- CT and MRI scans
We suggest that you dip in and read up on the bits that interest you now, and refer back when you encounter other tests at a later date.
Regular audiology updates
Building up a picture of your child’s specific deafness usually takes a variety of tests carried out over several months and sometimes years. It is like a jigsaw, with each piece of the jigsaw adding to the overall picture. Very small babies, and new hearing aid or cochlear implant users are likely to be seen by the audiologist every 3–4 months initially, dropping to every 6 months once the technology is used and programmed well.
It is important to remember that follow-up hearing tests continue to ensure that hearing levels have not changed and that hearing aids or electrodes are still functioning properly. With carefully selected and maintained technology, along with a good early intervention programme, you should be confident and optimistic about your child developing good listening and speech skills.
A consultant audiologist provides some general advice about hearing tests
Before we look in more detail at the different types of hearing test, watch this video of Consultant Audiological Scientist Huw Thomas providing some general advice about hearing tests.
Objective measures
Objective measures are tests that do not require the child to actively participate or cooperate – beyond remaining still, asleep or being sedated. As children do not have to report back to the audiologist, objective tests enable audiologists to assess much younger children and are now used routinely in newborn hearing screening programmes across much of the developed world.
We will now briefly explain the following types of objective hearing tests:
- Otoacoustic emissions (OAEs) testing
- Auditory brainstem response (ABRs) testing
- Otoscopy
- Tympanometry – acoustic immittance testing
- Acoustic reflex testing
Otoacoustic emissions testing
Otoacoustic emissions testing in young babies helps audiologists to determine whether the middle ear and outer hair cells of the inner ear are functioning well.
Otoacoustic emissions (OAEs) are sounds – a bit like little echoes – which appear in the ear canal when the hair cells in the cochlea in the inner ear are active. The emissions are also conducted through the middle ear. So, if we can detect otoacoustic emissions in response to sounds, this tells us that both the middle ear and outer hair cells of the inner ear are functioning well.
An otoacoustic emissions (OAE) test being performed on a baby
The detection of otoacoustic emissions is a very useful test to screen newborn babies – these tests are termed Otoacoustic emissions tests or OAE tests. (Sometimes they are called automated otoacoustic emissions tests or AOAE tests.)
This test should only take a few minutes if the baby is settled and there is little background noise. It does not cause any pain or discomfort and you can stay with your baby while it takes place. Generally the results of the test can be given to you at the time of testing.
During the OAE test, a series of tones are played in pairs into the baby’s ear. If both the middle ear and the outer hair cells in the cochlea are functioning properly the hair cells will produce a series of echoes in response to the tones. These are measured with a small probe that is placed in the baby’s ear canal.
The test results are either a pass (echoes are present) or a refer (echoes were not detected). A refer does not tell us the level of a child’s deafness, just that deafness is present. A pass result does also not confirm normal hearing at all frequencies.
OAE testing is not however entirely reliable within the at risk population of babies – such as those who are premature, have a low birth weight, or who are very poorly. Nor do OAEs tell us whether the auditory nerve pathways are working well. This is where auditory brainstem response testing is necessary to add to the picture.
Auditory brainstem response testing
Auditory brainstem response (ABR) testing determines how the brainstem (the auditory neural pathway to the brain) responds to sound.
A consultant audiologist explains auditory brainstem testing
In this video, Consultant Audiological Scientist Huw Thomas discusses auditory brainstem testing for infants.
During an ABR test, Four small sensors are attached with gel to specific places on the baby’s head and shoulder. Small headphones or inserts deliver sounds and the sensors pick up the auditory nerve’s electrical activity and send it to a computer for analysis. Lack of electrical activity may indicate a problem with the sensorineural pathway from the cochlea to the brain.
An auditory brainstem response (ABR) test being performed on a baby
ABR tests are used as a screening tool for hearing impairment in newborn babies. Screening staff on maternity wards or by Health Visitors in your home use an automated version of the testing equipment . Automated ABR tests can take between 5 and 30 minutes.
You can stay with your baby while an ABR test is being performed and it will not hurt or be uncomfortable for your baby. To achieve the current standard of recordings babies must be sleeping or sedated during ABR testing.
Auditory brainstem responses may also be tested through ‘air conduction’ and through ‘bone conduction.’ The difference between these two methods of testing is explained later in this paper.
Otoscopy
Otoscopy is the visual inspection of the outer ear, the ear canal and the tympanic membrane (ear drum) using an otoscope.
Inspecting a young child’s ear using an otoscope
An otoscope is a hand held instrument powered by batteries and containing a light and a magnifier. Babies (or children) just need to be still long enough for the audiologist or doctor to have a look down their ear canal.
Otoscopy is used to detect any abnormalities in the outer ear and ear canal, and assess the status of the eardrum.
A consultant audiologist explains how an otoscope works
In this video, Consultant Audiological Scientist Huw Thomas discusses how an otoscope or auriscope works.
Tympanometry
Tympanometry helps us know how well the eardrum and middle ear work.
The tympanometry test is part of the process if a baby is referred for further tests following newborn hearing screening. It is also an invaluable tool for checking the functioning of the middle ear throughout childhood (and for adults too).
Using tympanometry with a young child
In the tympanometry test, the audiologist places a small probe into the ear canal. The probe delivers a small puff of air to the eardrum whilst playing tones, and measures the amount the eardrum move in response. The frequency of sound played by the tympanometry probe is changed between low and high frequency depending on the age of the child.
All being well, the eardrum should move freely with the change of pressure. If the eardrum does not move freely, this indicates a problem of some form – such as fluid or negative pressure in the middle ear, a hole in the eardrum or a problem with the chain of small bones (the ossicles) in the middle ear.
Tympanometry therefore adds another piece to the jigsaw by telling us the state of another part of the ear – the middle ear.
A consultant audiologist explains typanometry
In this video, Consultant Audiological Scientist Huw Thomas discusses typanometry.
Acoustic reflex
The acoustic reflex can be measured with the same probe used for tympanometry.
The stapedial muscle in the middle ear moves in response to loud sounds. This reflex occurs in the majority of normally hearing ears but may not occur with middle ear disease or if sensorineural deafness of 40dBHL or greater is present.
Measuring the acoustic reflex on a young child
Behavioural testing
Behavioural testing cannot be used on babies and very young infants as it requires the child to cooperate by responding to the sounds they hear. Behavioural tests include:
- Behavioural observation
- Distraction testing
- Visual reinforcement audiometry (VRA)
- Conditioned play or performance audiometry
Behavioural testing is generally carried out in a soundproof booth at an audiology clinic. The most reliable results are obtained if one of the testers (audiologist or teacher of the deaf) sits across from the child. One tester will keep the child’s attention on the task and provide praise for each response, the other will administer the sounds and record responses on a special graph called an audiogram (see the next page for further information about audiograms).
Sound field and earphone testing
There are two main ways the audiologists can present sound to your child during a hearing test – sound field or earphones/inserts.
Fitting headphones/earphones small enough and encouraging young children to wear them can be a challenge so testing with younger children is often done by playing sounds through loudspeakers. This is referred to as ‘sound field testing’.
The main disadvantage of sound field testing is that it is not ear specific: both ears are tested at the same time. This means it is not possible with sound field testing to determine if one ear hears better than the other.
For this reason, it is beneficial to test using earphones or inserts (based on the child’s own ear moulds) as soon as the child will accept them, as this enables the tests to build up a picture of how each ear functions.
Hearing threshold
During hearing tests, the audiologists will try to measure your child’s hearing threshold – the softest sound to which your child responds.
During behavioural tests, sounds are played at hearing levels louder than the child can hear and made quieter as the child responds. The softest sound to which a child responds is referred to as the ‘hearing threshold.’ This hearing threshold is obtained at as many frequencies as the child has patience to discover. With very young children it will take a series of appointments over several months to achieve reliable and consistent responses for each ear, aided and unaided, across all the speech range.
Behavioural observation
When a baby hears a sound it is possible to observe his or her response by looking carefully for changes in behaviour. This is called behavioural observation.
From birth to around five months of age, responses to sound might include eye-blinking or eye-widening, startling, body movement, stilling, crying, cessation of crying or changes in sucking or breathing. Infants of five to six months (corrected for prematurity) are usually able to show they detect sounds by turning their eyes or head or by raising their head or vocalizing. A twelve month old may show detection of a sound by pointing to his or her ear.
The experience and skill of the audiologist, teacher or therapist presenting the sounds and observing the child’s response determines the success of behavioural observation testing. Even then it only provides a rough guide as to the level or frequency of the deafness.
Behavioural observations can however be very helpful additions to the information that parents and their support team give to audiologists as it can help them to determine the optimal programming of hearing aids or cochlear implants.
Distraction testing
Prior to newborn hearing screening, Health Visitors used distraction testing to screen all babies of 7-9 months of age and this is still typical in many countries where newborn hearing screening is not established.
The distraction test also helps to build up a picture of hearing levels across the speech range by audiologists testing in soundproof booths.Infants must be able to sit unsupported or with minimal support and have good head control; this usually means infants with a developmental age of at least 6-7 months. For this test, there is an upper age limit of 15-18 months.
In this procedure, one tester works on a small table in front of the child and uses a simple play activity (for example, spinning a toy) to distract the child as a second tester prepares to make a sound behind the child. The distractor phases out the action of the toy and observes the child’s response when the sound is played. The test then proceeds with further distraction and phasing out as another sound is played. Ideally, the child’s response should include a clear head-turn towards the source of the sound, but a partial turn, eye movement or stilling may be accepted. Infants with different degrees of deafness in each ear may turn , move or glance in the direction of their better ear even if the sound has been presented on the other side.
When distraction testing was used as a national screening test across the UK, many profoundly deaf infants were found to pass the test. Even by 9 months of age they could use additional clues to pass this form of hearing test. They turned in response to subtle changes in shadows and reflections (even in the eyes of the distracter), or a trace of perfume as the tester behind moved. As a result, more objective tests are preferred for newborn hearing screening and, instead, visual reinforcement audiometry (described below) is used more widely as a follow up test.
Visual reinforcement audiometry
Visual reinforcement audiometry is typically used from 9 months of age, when a child begins to turn his head to ‘look for’ a sound.
Visual reinforcement audiometry testing with a young child
Testing consists of using visual stimuli to reinforce the child’s response to sound. In the soundproof audiology test booth, boxes containing toys hidden behind dark glass are mounted on each side of the room beside a loudspeaker. A tone is played through one of the loudspeakers, and if the child looks in the direction of that sound, the box lights up and one of the toys is activated. The child learns that if he looks when the sound is presented, the toy will be activated. If he looks when there is no sound, nothing will happen.
Reliable and repeated responses using VRA can provide us with a much more detailed picture of what levels of sound a young child can hear at different frequencies across the speech range. Degrees of deafness from mild to moderate, severe or profound can be assessed without hearing aids, or to measure the benefit of using hearing aids or cochlear implants. Young children will require repeated appointments in order to build up all this information over time.
A consultant audiologist explains visual reinforcement audiometry
In this video, Consultant Audiological Scientist Huw Thomas discusses visual reinforcement audiometry.
VRA does not tell us precisely how well each part of the ear is functioning. Information from a variety of tests work together to give a clearer picture of your child’s deafness. For example, reliable responses through VRA could look the same if a child had a profound impairment in the cochlea or mixed deafness combining ‘glue ear’ with a severe sensorineural impairment.
Conditioned play audiometry
As a child approaches a development age of 2-3 years of age they can be taught to respond to play audiometry.
As with other behavioural tests, it is very helpful to have a test assistant who will teach the child this ‘listening game’. In this game, the child learns to hold a piece of a toy, such as one ring of a stacking toy or a brick, until he hears speech or a pure tone sound delivered through speakers or earphones. When the child hears the sound, he places the ring on the stick; the brick in a bucket; the man in the boat, etc. The audiologist determines the child’s thresholds in each ear for speech and for low- to high-pitch pure tone sounds.
Conditioned play audiometry – with headphones
Conditioned play audiometry – with speaker
Most children enjoy doing this test until they are 5-6 years of age, at which time they can raise their hand or press a button when they hear the sound, in the same way as when an adult’s hearing is tested.
Conditioned play testing is also used less formally in other situations using voice, specifically the Ling Six Sound Test with young children. We provide an explanation of what this test is later in the paper.
A consultant audiologist explains conditioned play audiometry
In this video, Consultant Audiological Scientist Huw Thomas discusses conditioned play audiometry.
Speech testing
Clicks and tones are a helpful start in the process of understanding if your child can hear and what they can hear. However, testing with just clicks and tones is a bit like looking at just the corners and the edges of the jigsaw, when what you really want to know is what the picture in the middle looks like.
Most babies with impaired hearing are born to parents with normal hearing levels who communicate through spoken language, and for those parents a key question is: “Can my young child learn to speak?” The page on understanding audiograms includes a section on mapping results of hearing tests in relation to the sounds of speech. This will also help you begin to answer this question.
Speech awareness
In speech awareness testing the audiologist is looking for the softest levels (hearing thresholds) at which a child can hear speech sounds.
The Ling Six Sound Test uses sounds that have energy at different frequencies across the speech range. Once you are aware of what those frequencies are, it can be used to assess how well a child is responding to your voice across the frequencies. This can be very helpful for checking if your child has a cold that is reducing his hearing levels slightly or if his hearing aids or implants are functioning well.
The Ling Six Sound Test
This Ling Six Sound Test is designed to provide information about your child’s ability to detect speech sounds in low, mid and high frequencies (pitch).
If your child can detect (hear) these sounds, he should be able to discriminate (understand) the sounds in spoken language.
The six sounds are delivered in normal speech without the opportunity for lip reading. They are:
- ah – as in father
- oo – as in moon
- ee – as in key
- mm – as in Mummy
- ss – as in sock
- sh – as in show
Speech discrimination
A child does not need to understand the words used in speech discrimination testing, he simply needs to repeat the speech sounds he hears.
Speech sounds are scored in terms of phonemes (the smallest units of sounds in a language), for example the word ‘cat’ is scored as the phonemes ‘c’ ‘a’ and ‘t’. This tells the audiologist, teacher or therapist which speech sounds a child can hear and imitate in this own speech and which sounds are systematically left out.
In order for a child to include a specific speech sound in his own speech, he must first hear that it is there in the speech of others. If a child routinely omits certain speech sounds, it may well be that he is not hearing them in the speech of others, in which case his hearing aids or implant may need to be adjusted or he may just need more time to practice listening to and making these speech sounds.
Speech reception/recognition
A child must know the names of some common objects before he can participate in speech reception testing.
Here the audiologist is looking for the softest level at which the child can recognize a familiar word. The audiologist would say a word like ‘cat’ and the child would be expected to point to the picture of a cat.Speech tests can be carried out in good acoustic conditions or in background noise. Audiologists tend to want to know what a child can hear with hearing aids in a good listening environment. Teachers tend to want to know how a child is hearing speech sounds in the livelier environment of a preschool or primary school class.
Air and bone conduction
Comparing results from tests using both air conduction and bone conduction can help the audiologist determine where deafness occurs in the ear. Auditory brainstem testing in babies can be undertaken using air conduction and bone conduction testing. Observational testing using visual reinforcement audiometry or conditioned play audiometry may also compare results from air and bone conduction testing. Speech Testing thresholds may also be determined both through air and bone conduction results.
Air Conduction
In air conduction testing, sound is played to the child through speakers, headphones, or insert headphones in the ear canal.
The sounds pass through the child’s outer ear, middle ear and inner ear (cochlea) and are carried to the brain by the auditory nerve. Deafness may be detected, but the impairment could be anywhere along that pathway from the outer ear to the inner ear, or it may be mixed deafness, combining both a middle ear and an inner ear impairment.
Further testing must be carried out to discover if the deafness is sensorineural (caused by damage to the cochlea or auditory nerve), or conductive (caused by problems in the outer or middle ears), or both.
How sound is transmitted through air-conduction-600w
Bone conduction
In bone conduction testing, a small vibrator is placed on the bone behind one ear; the vibrator is generally held in place by a headband.
The audiologist then presents sounds through the vibrating unit. Sounds are conducted through the vibrator and skull bone directly to the inner ear, by-passing the structures of the outer and middle ear. If a child is found to have a degree of deafness using air conduction, but normal hearing thresholds using bone conduction then we know that the problem is in the outer or middle ear and that the inner ear is healthy.
How sound is transmitted through bone conduction
The air-bone gap
The air-bone gap is the the difference between results obtained through air and bone conduction tests.
Sometimes the ‘air–bone gap’ is larger than audiologists would expect. This means that the difference between results obtained through air and bone conduction is not entirely explained by middle ear (conductive) deafness, and that the child may also have inner ear (sensorineural) deafness:
- Middle ear (conductive) deafness is almost always medically or surgically treatable in the longer term, or may be temporary due to glue ear in the shorter term.
- Inner ear (sensorineural) deafness is always permanent, but can be greatly helped by early intervention and appropriate technology.
Scans
As part of your child’s hearing assessments they may have a medical evaluation by an ear, nose and throat doctor (otolaryngologist). This evaluation may include a CT scan and an MRI scan of the brain and the middle and inner ear.
MRI scans
A magnetic resonance imaging (MRI) scan of the head is a non-invasive method to create detailed pictures of the brain and surrounding nerve tissue.
Several sets of images are usually required so the MRI scan can take between 2-15 minutes. As with a CT scan, your child will have to lie still during the scan, so he may be given a mild sedative.
MRI scans provide detailed pictures of the brain and nerve tissue that cannot always be seen on CT scans so often a child will have both prior to cochlear implant insertion.
CT scan
A computer tomography (CT) scan uses x-rays to create cross-sectional images of the inside of the body. CT scans give the doctor detailed pictures of the inner ear structure, and they are often used to determine whether a child is a suitable candidate for cochlear implants.
The CT scan does not hurt in any way and usually lasts a few minutes. However, your child will have to lie very still during the scan, so sedation is usually required. Your child will also not be able to eat or drink in the hours before the test.
