Understanding audiograms
After your child’s hearing tests, your audiologist will provide you with an audiogram – this is a graph which shows your baby’s level of deafness measured in that particular test. Over time, your child’s audiograms from a range of tests will help you and your audiologist get a full picture of your child’s deafness. This page helps to explain how to make sense of an audiogram – again we have kept all of his information on a single page so it is easier for you to bookmark and find at a later date.
What is an audiogram?
An audiogram is a chart which shows your child’s responses to various sounds during a hearing test. It records two aspects of sound:
- pitch (also known as frequency)
- loudness ( also known as intensity)
An audiogram is a written record of your child’s hearing levels that will build up over time, as different tests can be used and as your baby becomes older.
Each time there is a hearing test, it is a good idea to ask for a copy of your child’s results or audiogram. Keep these on file so you can watch how the picture builds up over time. You will need to make sure you are comparing like with like, as different tests may record results in slightly different ways. Ask your audiologist to explain these to you each time and this will help you to understand more at each visit.
A consultant audiologist explains the key features of an audiogram
In this video, Consultant Audiological Scientist Huw Thomas explains the key parts of an audiogram.
Understanding the key parts of an audiogram
Pitch or frequency
Audiograms show pitch or frequency from left to right.
Like on a piano keyboard, the low pitched (or low frequency) sounds are on the left of the audiogram moving through to high pitched (higher frequency) sounds on the right. Audiology tests usually use the term frequency rather than pitch – but they mean the same thing. We measure pitch/frequency in Hertz (Hz) – for example ‘1000Hz’.
Audiograms show pitch/frequency from low sounds on the left to high sounds on the right
Most speech sounds fall within the range between 250Hz to 6000Hz, but individual speech sounds have different bands of energy at different frequencies:
- Vowels tend to have a lot of low frequency energy as do some consonants such as ‘m,’ ‘b’ and ‘n’.
- Other consonants such as ‘s,’ ‘f’ and ‘th’ have more energy in the very high frequencies.
This can be illustrated by what is known as a ‘speech banana’ on the audiogram (shown at the end of this page).
Loudness or intensity
The numbers from top to bottom on an audiogram correspond to how loud sounds are, from quiet/soft at the top to loud at the bottom.
Audiograms show quiet sounds at the top and loud sounds at the bottom
The loudness of a sound is also referred to as the intensity of a sound and the unit of measurement is the decibel (dB). Sounds are not recorded beyond 120dB as they are so loud that you can feel them as well as hear them – in scientific terms they are at a “vibrotactile” level. As a rough guide, our speech is around:
- 40dB for quiet speech
- 50dB for conversational speech
- 60dB for loud speech
- 70dB for shouted speech
Hearing levels
Audiologists use standard definitions to describe hearing levels from normal to profound deafness.
In the UK standards are defined by The British Society of Audiology using these threshold levels (i.e. the quietest sound the individual can hear):
- Normal hearing: 0-20 dB threshold level
- Mild deafness: 21-39 dB threshold level
- Moderate deafness: 40-69 dB threshold level
- Severe deafness: 70-90 dB threshold level
- Profound deafness: in excess of 90 dB threshold level
Threshold hearing levels for the different categories of deafness
These descriptors are based on the average hearing threshold levels at 250 Hz, 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz in the better ear.
Hearing thresholds
The quietest sounds we can hear are recorded as our hearing thresholds.
These sounds are typically within 0–20dB for children, they may drop a little as we get older, and considerably more in our senior years. During hearing tests, the audiologist aims to record the quietest sounds your child can detect, but it takes time and skill to establish reliable hearing thresholds across the frequencies with babies and toddlers who cannot report precisely what they are hearing. The audiologist is likely to use different tests over a period of time to help find out your child’s thresholds.
Symbols
All audiograms use consistent symbols to record hearing levels in each ear
- circles (red when in colour) to mark responses from the right ear
- crosses (in blue when in colour) to mark responses from the left ear.
The easiest way to remember which symbol is for which ear is to use the three Rs: right = round + red
Other symbols used on audiograms might include triangles that denote unmasked bone conduction results. Soundfield testing may be marked with an ‘S’ or an ‘A’ when the child is aided or simply shown as a table of numbers. We explain these in more detail later in this page.
Familiar sounds audiogram
The ‘familiar sounds audiogram’ will help you relate your child’s hearing test audiograms to speech and everyday sounds.
The familiar sounds audiogram is a one page diagram which shows the loudness and pitch of some common sounds (such as a vacuum cleaner, a dog barking or a motorbike’s engine). It also shows the ‘speech banana’ which includes the common sounds of everyday speech.
The Familiar Sounds Audiogram – showing the speech banana
The familiar sounds audiogram can be particularly helpful alongside your child’s audiograms when trying to explain your child’s degree of deafness to other members of your family or others supporting your child.
Some typical audiograms
We will now show you some example audiograms showing different types of deafness.
Example 1 – Bilateral deafness
The audiogram below records the responses of a child who has a two-sided (or bilateral), relatively flat, moderate deafness. Hearing thresholds in both the right (circles) and left (crosses) ears are between 51 and 70dB across the frequencies. Hearing levels in the child’s right ear is very slightly better than in the left.
Audiogram showing moderate deafness in both ears
Example 2 – Uneven, bilateral deafness
We would describe the child with the audiogram below as having a moderate deafness, as the average thresholds in the better ear are between 41 and 70dB. When a child does not have similar deafness in both ears (as shown in Example 1 above), it is often as well to describe each ear separately, e.g. this child has moderate deafness in his left ear, but is profoundly deaf on the right.
Audiogram of a child with moderate deafness in the left ear and profound deafness in the right ear
Air and bone conduction audiograms
Your audiologist may use a combination of air conduction and bone conduction testing. In air conduction testing, sounds are presented to the eardrum, are conducted through the middle ear to the cochlea. In bone conduction testing sound vibrations bypass the middle ear and are taken direct to the cochlea.
Comparing the results of air and bone conduction testing can help the audiological team to determine where a child’s hearing difficulty lies. Different symbols represent results from these two types of testing with circles and crosses marking air conduction results and brackets used for bone conduction results. We will now take a look at some example audiograms comparing bone and air conduction test results.
Example 1 – Conductive deafness
This audiogram is typical of a child with moderate conductive deafness.
Audiogram showing conductive deafness in left ear
The blue crosses indicate moderate deafness in the left ear using an air conduction test via headphones / speakers. The brackets represent normal levels of hearing when bone conduction is used. This combination indicates that the child’s inner ear is working normally, but that sound cannot get through the middle ear.
Example 2 – Sensori-neural deafness
The audiogram below is typical of a child with sensori-neural deafness in the right ear.
Audiogram showing sensori-neural deafness in a child’s right ear
There is little difference between the red circles of the air conduction and brackets of the bone conduction testing.
Example 3 – Mixed deafness
The audiogram below shows ‘mixed’ deafness – there is both permanent sensori-neural deafness and a (possibly temporary) middle ear problem.
Audiogram showing mixed deafness in a child’s right ear
Both the air and the bone conduction results indicate deafness in the right ear. As there is a significant gap between the results, this indicates sensori-neural deafness with overlying conductive deafness, possibly due to glue ear.
Aided audiograms
The audiograms above help us to understand the sounds your child can detect without his hearing aids or cochlear implants. This is a necessary starting point but it would also be helpful to know how your child hears with his hearing aids or cochlear implants.
A consultant audiologist discusses aided and unaided audiograms
In this video, Consultant Audiological Scientist Huw Thomas explains describes the importance of aided and unaided audiograms.
Aided audiograms tell us whether or not your child can access all of the sounds of speech when they are using their hearing technology. Again it takes time, patience and several visits to the audiology clinic to build up results in each ear, across the speech spectrum, unaided and aided. As you help to your child develop their listening skills this should also help improve the results slightly.
Example – aided audiogram
The audiogram below indicates that this child has a profound deafness in his left ear.
An aided audiogram showing a child’s aided and unaided hearing in their left ear
Using digital hearing aids he can detect some low frequency sounds which should help him to detect most vowel sounds. However, he has no useful amplified hearing in the mid to high frequencies and will therefore have difficulty learning to use those sounds in his own speech.
His subsequent cochlear implant map enables him to detect sounds right across the speech frequencies at levels typical of a child with only a mild deafness.
Implications for speech – the ‘speech banana’
The ‘speech banana’ shows the area on an audiogram where the sounds of conversational level speech have most of their energy. The audiogram below superimposes the speech banana on the previous audiogram.
Aided audiogram with speech banana superimposed
The aim of hearing aid or cochlear implant programming is to help your child hear sounds within the speech banana clearly. It is clear from the current example that this little boy could not do so unaided or using the most powerful hearing aids, however, with a cochlear implant he can detect all the sounds of speech when the speech signal is close and clear.
A consultant audiologist explains the location of common speech sounds on audiograms
In this video, Consultant Audiological Scientist Huw Thomas explains the location of common speech sounds on audiograms in the ‘speech banana’.
To sum up…
Understanding audiograms and hearing tests is not easy! It takes the professionals many years of training so do not expect to understand everything all at once. Take time, ask questions and do not be afraid to ask if you need your audiologist to repeat information!
