You have just finalized your hearing test. The hearing specialist is now coming into the room and presents you with a graph, like the one above, except that it has all of these signs, colors, and lines. This is intended to demonstrate to you the exact, mathematically precise characteristics of your hearing loss, but to you it might as well be written in Greek.
The audiogram contributes confusion and complication at a time when you’re supposed to be focusing on how to improve your hearing. But don’t let it trick you — just because the audiogram looks puzzling doesn’t mean that it’s hard to grasp.
After reading through this article, and with a little terminology and a handful of basic concepts, you’ll be reading audiograms like a expert, so that you can concentrate on what really counts: better 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.
Understanding Sound Frequencies and Decibels
The audiogram is really just a chart 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, weak sound. As you move down the line, the decibel levels increase, standing for progressively 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 move along the horizontal axis to the right, the frequency will steadily increase until it arrives at 8,000 Hz. Vowel sounds of speech are typically low frequency sounds, while consonant sounds of speech are high frequency sounds.
And so, if you were to begin at the top left corner of the graph and draw a diagonal line to the bottom right corner, you would be raising the frequency of sound (shifting from vowel sounds to consonant sounds) while raising the volume of sound (moving from fainter to louder volume).
Testing Hearing and Marking Up the Audiogram
So, what’s with all the markings you usually see on this basic graph?
Easy. Start at the top left corner of the graph, at the lowest frequency (125 Hz). Your hearing specialist will present you with a sound at this frequency through headsets, beginning with the lowest volume decibel level. If you can hear it at the lowest level (0 decibels), a mark is made at the joining of 125 Hz and 0 decibels. If you can’t perceive the 125 Hz sound at 0 decibels, the sound will be presented once more at the next loudest decibel level (10 decibels). If you can perceive it at 10 decibels, a mark is made. If not, carry on to 15 decibels, and so on.
This exact routine is done again for each frequency as the hearing specialist progresses along the horizontal frequency axis. A mark is created at the lowest perceivable decibel level you can perceive for every sound frequency.
Regarding the other symbols? If you notice 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 regularly used to mark the points for the left ear; an O is applied for the right ear. You may discover some additional symbols, but these are less important for your basic understanding.
What Normal Hearing Looks Like
So what is seen as normal hearing, and what would that look like on the audiogram?
Individuals with healthy hearing should be able to perceive each sound frequency level (125 to 8000 Hz) at 0-25 decibels. What would this look like on the audiogram?
Just take the empty graph, find 25 decibels on the vertical axis, and sketch a horizontal line entirely across. Any mark made beneath this line may indicate hearing loss. If you can perceive all frequencies below this line (25 decibels or higher), then you probably have normal hearing.
If, however, you can’t perceive the sound of a particular frequency at 0-25 dB, you very likely have some form of hearing loss. The smallest decibel level at which you can perceive sound at that frequency determines the grade 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 smallest decibel level at which you can perceive this frequency is 40 decibels, for instance, then you have moderate hearing loss at this frequency.
As a summary, here are the decibel levels connected with normal hearing along with the levels correlated 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 marks of hearing loss look like? Because many instances of hearing loss are in the higher frequencies (referred to as — you guessed it — high-frequency hearing loss), the audiogram would have a downward sloping line from the top left corner of the graph sloping downward horizontally to the right.
This indicates that at the higher-frequencies, it requires a progressively louder decibel level for you to perceive the sound. And, considering that higher-frequency sounds are connected with the consonant sounds of speech, high-frequency hearing loss damages your ability to understand and follow conversations.
There are a few other, less common patterns of hearing loss that can show up on the audiogram, but that’s probably too much information for this article.
Test Your New-Found Knowledge
You now know the nuts and bolts of how to read 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.