When you complete a hearing test your audiologist will hand you the test results in the form of an audiogram. The graphs, crosses, circles and lines may look a little confusing at first but the test results are really not that daunting. And understanding your hearing test will help you make really well-informed decisions about the best treatment for your needs.
What then does a hearing test measure and how do you interpret the results? Your audiologist may conduct a number of tests but the most common tests use pure tones and speech sounds to test your ability to hear across the full range of sounds.
What do the test results look like?
Your audiologist will mark your hearing test results on a graph that will look something like this.
The left axis indicates the intensity or volume of the test sounds that were played to you during the test going from softest at the top to loudest at the bottom. It’s measured in decibels (dB). As a general guide a whisper is around 30 dB whereas a snowmobile might measure around 135dB. You can check out how loud other sounds are here.
The right axis marks the frequency or pitch of the sounds. This measurement of sound waves is measured in hertz (Hz) or kilohertz (kHz) and indicates the number of cycles per second. The name comes from the German scientist Heinrich Hertz who did pioneering research into electromagnetic waves in the 1880s.
Normal hearing ranges from 20 Hz up to 20,000 Hz but the most sensitive hearing range for the average person lies between 2000 and 5000 Hz. Obviously, volume of sound also plays an important part in whether you can hear the sound or not so your hearing test results will measure a combination of both frequency and volume.
During the test your audiologist will play pure tones at differing frequency and volume levels through headphones and plot your response to these on the graph. They will then compare your results against a standardised minimum audibility curve to analyse the degree and nature of your hearing loss.
What do the circles and lines mean?
Standard audiometric tests use red circles to indicate the right ear results and the blue crosses to mark your left ear results. Each circle or cross indicates both the frequency level tested and the volume level at which you were able to hear that frequency.
Results in the top 5th of the graph indicate normal hearing so a person with normal hearing should be able to hear all those sounds from 250 to 8000 Hz at very quiet volume levels. Those areas where your test lines drop below that 20dB range indicate hearing loss.
The greater the drop the more severe is the hearing loss. The graph below shows how hearing loss severity is measured from normal through to profoundly deaf.
People are often surprised by the shape of their hearing test curve. This is because hearing loss can be quite gradual and with the brain’s marvellous ability to adapt to the loss it may not be noticeable for some time.
Typically, people tend to lose sensitivity in the higher frequencies first. This is because the high frequency hair cells are more easily damaged due to their position in the cochlea than low frequency hair cells. Typical high frequency hearing loss can be cause by the aging process, ototoxic drugs and noise.
You might see other symbols on your test too such as < > or [ ] to indicate bone conduction tests. Typically, both left and right ears will show a similar pattern of deterioration with normal age-related hearing loss but asymmetrical or unusual test curves may indicate other causes that need to be explored.
How do the test results show difficulties with speech?
Difficulties understanding conversations may be the first sign of hearing loss for many people. Your test results will give a very clear picture of just why you might be struggling with speech comprehension.
Normal conversation is around 60dB but even moderate hearing loss may create some difficulties with understanding speech. High frequency hearing loss especially can cause problems with understanding conversation because many speech sounds such as S, H, and F are in the high frequency range.
The harder consonants such as K and T are usually more clearly heard but background noise may make even these sounds hard for you to pick up at times.
In addition to pure tone tests your audiologist will probably also carry out some speech testing or word recognition testing where you may hear spoken words through the headphones. Your results will be recorded in a separate box as a percentage based on how often a word needs to be repeated before you can understand it.
So what do my results indicate?
Most people will see a downwards curve especially towards the higher frequencies. The really critical thing to notice is at what volume that curve starts and how steeply it drops off. You can work out the overall degree of your hearing loss from mild to profound by calculating the average of your hearing test readings.
So for the audiogram above the hearing loss for the left ear would be 20 + 20 + 20 + 35 + 40 + 70 + 80 + 80 ÷ 9 = 40.5.
Your audiologist should explain just what your test results mean and you need to ask any questions you have. But being prepared with a deeper understanding of test results can help you to ask really vital questions about your treatment. It’s important for you to be in control of your process as you come to terms with hearing loss and having a clearer understanding of what your hearing test results mean can make a big difference.