You’ve just completed your hearing test. The hearing specialist is now coming into the room and provides you with a graph, like the one above, except that it has all of these signs, colors, and lines. This is supposed to reveal to you the exact, mathematically precise characteristics of your hearing loss, but to you it might as well be written in Greek.
The audiogram creates confusion and complexity at a time when you’re supposed to be directing your focus on how to improve your hearing. But don’t let it deceive you — just because the audiogram looks confusing doesn’t mean that it’s difficult to interpret.
After reading through this article, and with a little vocabulary and a few basic principles, you’ll be reading audiograms like a expert, so that you can focus on what really counts: healthier hearing.
Some advice: as you read the article, reference the above blank audiogram. This will make it easier to comprehend, and we’ll tackle all of those cryptic marks the hearing specialist adds later on.
Understanding Sound Frequencies and Decibels
The audiogram is really just a diagram that records sound volume on the vertical axis and sound frequency on the horizontal axis. (are you having flashbacks to high school geometry class yet?) Yes, there’s more to it, but at a basic level it’s just a chart graphing two variables, as follows:
The vertical axis documents sound intensity or volume, measured in decibels (dB). As you move up the axis, the sound volume decreases. So the top line, at 0 decibels, is a very soft, faint sound. As you go down the line, the decibel levels increase, representing gradually louder sounds until you get to 100 dB.
The horizontal axis records sound frequency, measured in Hertz (Hz). Starting at the top left of the graph, you will see a low frequency of 125 or 250 Hz. As you keep moving along the horizontal axis to the right, the frequency will gradually increase until it reaches 8,000 Hz. Vowel sounds of speech are generally low frequency sounds, while consonant sounds of speech are high frequency sounds.
So, if you were to start at the top left corner of the graph and draw a diagonal line to the bottom right corner, you would be increasing the frequency of sound (going from vowel sounds to consonant sounds) while raising the strength of sound (moving from fainter to louder volume).
Evaluating Hearing and Marking Up the Audiogram
So, what’s with all the markings you usually see on this simple chart?
Easy. Start at the top left corner of the graph, at the lowest frequency (125 Hz). Your hearing professional will present you with a sound at this frequency through earphones, beginning with the smallest volume decibel level. If you can hear it at the lowest level (0 decibels), a mark is created at the intersection of 125 Hz and 0 decibels. If you are not able to perceive the 125 Hz sound at 0 decibels, the sound will be provided once more at the next loudest decibel level (10 decibels). If you can hear it at 10 decibels, a mark is created. If not, advance on to 15 decibels, and so on.
This identical technique is done again for every frequency as the hearing specialist moves along the horizontal frequency axis. A mark is created at the lowest perceivable decibel level you can perceive for every sound frequency.
In terms of the other symbols? If you observe two lines, one is for the left ear (the blue line) and one is for the right ear (the red line: red is for right). An X is most often applied to mark the points for the left ear; an O is used for the right ear. You may discover some other characters, but these are less vital for your basic understanding.
What Normal Hearing Looks Like
So what is regarded as normal hearing, and what would that look like on the audiogram?
Individuals with normal hearing should be able to perceive each sound frequency level (125 to 8000 Hz) at 0-25 decibels. What might this look like on the audiogram?
Take the blank graph, find 25 decibels on the vertical axis, and draw a horizontal line completely across. Any mark made underneath this line may display hearing loss. If you can perceive all frequencies below this line (25 decibels or higher), then you probably have normal hearing.
If, on the other hand, you cannot perceive the sound of a particular frequency at 0-25 dB, you probably have some form of hearing loss. The lowest decibel level at which you can perceive sound at that frequency determines the degree of your hearing loss.
By way of example, take the 1,000 Hertz frequency. If you can perceive this frequency at 0-25 decibels, you have normal hearing for this frequency. If the lowest decibel level at which you can hear this frequency is 40 decibels, for instance, then you have moderate hearing loss at this frequency.
As an overview, here are the decibel levels identified with normal hearing along with the levels linked with mild, moderate, severe, and profound hearing loss:
Normal hearing: 0-25 dB
Mild hearing loss: 20-40 dB
Moderate hearing loss: 40-70 dB
Severe hearing loss: 70-90 dB
Profound hearing loss: 90+ dB
What Hearing Loss Looks Like
So what would an audiogram with indications of hearing loss look like? Since the majority of instances of hearing loss are in the higher frequencies (labeled as — you guessed it — high-frequency hearing loss), the audiogram would have a downward slanting line from the top left corner of the chart slanting downward horizontally to the right.
This means that at the higher-frequencies, it requires a progressively louder decibel level for you to experience the sound. Furthermore, seeing as higher-frequency sounds are linked with the consonant sounds of speech, high-frequency hearing loss impairs your ability to understand and follow conversations.
There are a few other, less prevalent patterns of hearing loss that can manifest on the audiogram, but that’s probably too much detail for this article.
Testing Your New-Found Knowledge
You now know the essentials of how to interpret an audiogram. So go ahead, schedule that hearing test and impress your hearing specialist with your newfound talents. And just think about the look on their face when you tell them all about your high frequency hearing loss before they even say a word.