reading your audiogram
Reading Your Audiogram was originally published as a post by Kim Ward in June of 2008, is still getting many views and the info remains vital to anyone who has hearing loss. We hope anyone wanting to understand what the information on an audiogram means finds this helpful!
Last month I completed a project on audiograms for a class. Realizing many people with hearing loss don’t understand what all the symbols mean, I thought I’d condense it into a blog. I am not an audiologist, or an “expert” on audiograms. I’m just a person with hearing loss, so if something doesn’t make sense, I suggest you ask your audiologist. This is a very short and simplified overview. I’ve also included links at the bottom of the page for further reading.In order to understand an audiogram, first you need to understand sound. There have been entire books written about sound alone, but I’m going for simplicity here.
Why does a bird sound different from a frog?
Sounds vibrate at different speeds. Low sounds vibrate more slowly than high sounds. Here is an illustration of low frequency sound (on the top) vs high frequency (on bottom).
Pitches tested on an audiogram may range from 125 hertz to 8000 hertz. The vertical lines of the audiogram indicate pitch. 125 hertz is a low-pitched sound, while 8000 hertz is high-pitched.
The piano is a great way to illustrate low-pitched vs high-pitched sounds. Of course many sounds are lower or higher than the lowest and highest piano keys. Additionally, there are pitches between each key. Audiologists do not measure every single pitch; they only measure a few pitches at certain intervals to give them an idea of how you might be affected by hearing loss.
Audiogram of familiar sounds
You already know some sounds are loud and some soft. A loud bus can sound soft in the distance. It becomes louder as it gets closer. It is the same sound near or far; only the intensity has changed. The loudness or intensity of a sound is measured in decibels (dbs). Below, the horizontal lines of the audiogram represent the loudness of sounds (decibel intensity).
This makes perfect sense if you think about it. When you turn the volume up on your CD player, the pitch of the music you’re listening to stays the same. You recognize a piece of music whether the volume is high or low, unless it’s too low to hear. Intensity levels measured on audiograms range from about 5 decibels (very soft) up to 120 decibels (very loud).
Putting it all together, your audiogram may look like this if you have good hearing:
Everything above the blue and red lines (the hearing threshold) is what you don’t hear in each ear. Everything below the lines is what you hear. The audiogram above represents good hearing because the hearing threshold falls at or above 10dbs in all the pitches tested.
The Speech Banana
Misunderstanding speech is what sends many of us to the doctor when we first begin losing our hearing. As you can see, some sounds like ‘th’ and ‘s’ fall in the high pitch ranges, while other sounds like ‘m’ and u’ fall in the low pitch areas.
Many people have significant hearing loss in some pitches while their hearing remains good in other pitches. Depending on your hearing loss, you may have difficulties hearing high pitched sounds or low pitched sounds. The speech sounds you hear well may drown out the speech sounds you don’t hear. This is why, when we lose our hearing, we may feel like we hear a lot of sound, but there is no clarity. We only hear some sounds. Also, the ability to hear sometimes and not other times may lead others to think we have “selective hearing.” We actually can hear better sometimes, depending on what is said.
Your exposure to language and when you lost your hearing matters
Some people place the number of English phonemes at around forty, but others say it is impossible to know how many phonemes there are because of all the different English dialects. Your hearing threshold and exposure to various dialects can impact understanding when you have hearing loss. Also, when you lose your hearing makes a difference. Babies who lose their hearing pre-lingually have difficulty learning to understand speech.
We are all different
Any two people with the exact same hearing thresholds may not hear exactly the same way. This can be hard for some to understand, but think about runners. All feet are different. Some people have flat feet, some don’t, some people are bow-legged, some may have scar tissue from old injuries, some legs are short and others long. Many factors determine how fast you run. It’s the same with hearing. Many factors determine how well you understand the sounds you hear besides measurements plotted on an audiogram.
When people lose their hearing they don’t necessarily lose all their pitches equally. A common type of hearing loss is the “ski-slope” where low tones remain intact, while high tones drop. There is also a reverse ski-slope, a “cookie bite” and reverse cookie bite.
Why does this happen? If you look at the picture of the cochlea below, you will notice different areas of the cochlea are responsible for detecting different frequencies.
Often the nerves in only one area of the cochlea are damaged, while other nerves remain healthy. A similar analogy would be experiencing numbness in just one part of your leg after having a bad accident.
During sickness, parts of the cochlea may become damaged. Those parts may not react to sound unless amplified. When a hearing loss becomes severe to profound, amplification may no longer do the job adequately. A person can begin to experience pain with loud amplification while simultaneously unable to hear– especially when other parts of the cochlea still work just fine. The cochlea has become dysfunctional.
Ski slope hearing loss
Below is an example of the common ski-slope hearing loss. The slope can be steeper or less steep. Notice the severe hearing loss at 4000 hertz, but “normal” hearing at 1000 hertz. Without hearing aids, this person will hear ‘m’ and ‘u’, but not ‘f’ or ‘s’. Listening to speech becomes a constant game of fill-in-the-blanks.
The circles indicate measurements for the right ear.
The x’s indicate measurements for the left ear.
What are the brackets on an audiogram? While the “air conduction” test determines hearing threshold (the blue line below), audiologists also perform a bone conduction test, with a vibrator placed near the cochlea. This can help the audiologist determine whether there’s a problem with the cochlea or some other part of the ear. The brackets indicate the results of the bone conduction. They usually look like this > but sometimes they look like this ].
Below there’s a disparity between the bone conduction and air conduction results. The cochlea seems to be working fine, as shown by the brackets. In this case, doctors determined it was due to infection of the middle ear.
The SayWhatClub is an online international nonprofit that offers peer-to-peer support to its subscribers with hearing loss. For more information, please visit our home page at www.saywhatclub.org
For Further Reading: