An audiogram is the graph plotted by an Audiologist when a hearing test is performed. Quite simply, it shows the softest sounds you can hear. As there is often a lot of information given during the initial test appointment (test results, coming to terms with the fact you have a hearing loss and may need a hearing aid, hearing aid information itself, financing or funding options for hearing aids) it’s no wonder it can be hard to remember what everything means!
For a quick hearing test or screening, this audiogram may be the only information gathered about your hearing. If you have a more comprehensive assessment there may be other information as well including speech test results and middle ear results. Some clinics are happy to provide you with your audiogram, whereas others may request you obtain this through your GP if you have had a medical referral for a hearing test.
If we look at the basic audiogram, it is a graph with two axes. Top to bottom is the volume of sound going from soft up the top to loud down the bottom. Sound is measured in decibels relative to hearing levels, or dB HL, where 0 is the threshold of normal hearing (Interacoustics, March 2016). Although 0 is where normal hearing starts, the normal range of hearing is actually from 0 to 20, and this normal range is the same no matter what age you are.
Across the graph from left to right is frequency or pitch of sound. This is measured in Hertz (Hz) or Kilohertz (kHz) for the higher frequencies. Think of a piano keyboard that goes from bass to treble if you sweep your finger left to right – the audiogram is effectively the same. Most speech sounds fall between the range of 500-4000Hz and the frequency range for a hearing test is usually 250-8000Hz. In rare cases either lower frequencies (down to 125Hz) or higher frequencies (up to 12kHz) may also be tested depending on the purpose of the test.
The audiogram should have a table nearby explaining what the symbols plotted on the graph mean. Circles indicate the right ear, crosses indicate the left ear. If your audiogram is in colour: red is for right and blue for left. A basic hearing screening will only have these symbols, but a comprehensive test will also have other symbols such as < or >, [ or ] or Π, sometimes there are even letters printed on the audiogram! What do they all mean?
Circles and crosses (even filled in circles and crosses) are air conduction results, which are from headphones or earphones. These indicate how loud you can hear sound when it goes through all 3 parts of your ear (outer, middle and inner) and is the primary measure of the softest sounds you can hear.
The different types of brackets indicate bone conduction which was the tight headband you may have worn that sat behind your ear – this bypasses the outer and middle ears and sends the sound directly into the cochlea in your inner ear. Bone conduction is normally performed during a comprehensive hearing test and indicates what part of your ear the hearing loss is in – and can often help your Audiologist to know whether any medical treatment should be considered rather than just a hearing aid. As a rule if the bone conduction is much higher on the audiogram than the air conduction this could indicate a conductive or mixed hearing loss, and medical referral should be undertaken to investigate the cause and any treatment, especially if a hearing aid is being considered.
On your audiogram there might be different letters printed, or a banana shape or shaded area. This area is where the different speech sounds occur, and each letter is actually a speech sound - so you can see for yourself what sounds you can hear and which you can’t – at a normal conversational volume. This can help you make sense of what your audiogram actually means! If your hearing levels (circles and crosses) are above the letter then you can hear it well, if your hearing is below the letter then you can’t hear that sound well unless it is made louder in volume. You may see that your audiogram is a mix - some speech sounds you can hear well (typically vowels and sounds like M, N, D) and some you may not hear well (typically F, S, TH). This is why people frequently say “I can hear but not understand” as they are not hearing all the sounds they need for speech to make sense.
As mentioned above, the range of normal hearing is from 0 to 20dB. If any results fall below 20 this indicates a hearing loss. Below normal hearing is graded by the terms mild, moderate, severe and profound. Mild is down to 45, moderate to 70, severe to 90 and profound below this. Hearing is not explained using a percentage which is a common misunderstanding, it will be described using these terms (for example mild to moderate, moderate to severe etc).
The most common shape for a hearing loss is where it slopes downwards towards the right, meaning that higher pitched (treble) sounds are harder to hear. This is typically what happens with age and exposure to loud noise. Hearing loss does vary from person to person with some people having flat hearing losses and others having a reverse slope where the deeper sounds are worse and the audiogram slopes upwards from left to right. Often left and right ears are similar on the audiogram, but if one ear is worse, then that line will be below the other on the audiogram.
If you were given a speech test where you heard a man’s voice say words you then had to repeat, then this will be the percentage you were given, which is often confused with your hearing levels. This percentage score is called speech discrimination and what this actually means is how clearly you can hear speech when the sound is made loud enough for you. The volume that you hear the words is usually dependent on your audiogram therefore for some people these words may be at a normal conversational speech volume, whereas for others the volume of speech may be made quite loud. This score is a good indicator of your overall hearing ability, and if you have a hearing loss then it can indicate how well you are likely to do with a hearing aid.
As hearing is complex and not about simply turning up the volume, if you have average speech discrimination then a hearing aid won’t be the answer to your hearing difficulties by itself. For example, if you have a severe hearing loss and your speech discrimination for amplified speech is only 60%, then even with a hearing aid you will still have difficulty understanding what people say. Unfortunately, generally the poorer your hearing is the worse your speech discrimination is; and the longer your leave your hearing loss untreated (without a hearing aid) the worse your speech discrimination is likely to get in the long run.
So how do you know whether you actually need a hearing aid? Generally if your audiogram shows you are missing many or most of the speech sounds, or you are well below the normal hearing range (20dB or lower on the graph) a hearing aid may benefit you.
There has been abundant research into early intervention for hearing loss and fitting hearing aids to people even with a mild hearing loss. The biggest finding has been from The Lancet International Commission on Dementia Prevention and Care, where untreated hearing loss in middle age was found to be the single biggest modifiable risk factor for cognitive decline later in life (Livingston, et al., 2017).
Even for a mild hearing loss a hearing aid can make a big difference to your communication and levels of fatigue by the end of the day. Certainly if the hearing loss is more than mild a hearing aid should be considered as an option. As technology improves, hearing aids are becoming smaller in size, and there are even completely invisible shower-proof hearing aids available!
Your Audiologist can discuss suitable hearing aid options with you based on your hearing ability, your individual ear, and your needs and lifestyle. It is also important to have realistic expectations of what hearing aids can and cannot do, so you know what to expect. Your Audiologist can also discuss finance and funding options available for hearing aids. Many clinics have interest free finance packages available and many private health funds offer a rebate on hearing aids if you have extras cover. In Australia, if you are on a pension or DVA funded you may be eligible for hearing aids through the Hearing Services Program.
Understanding your own audiogram is easy, and is an important step to help you take control of your communication needs, especially when considering a hearing aid. If you have any questions when looking at your audiogram or other results, or want to discuss hearing aid options, your Audiologist at Attune Hearing will be more than happy to help.
References
Interacoustics. (March 2016). The Variety of Decibel - Basics. Retrieved from https://www.interacoustics.com/guides/basics/the-variety-of-decibel-basics
