You have just concluded your hearing test. The hearing instrument specialist is now coming into the room and provides you with a graph, like the one above, except that it has all of these characters, colors, and lines. This is supposed to present to you the exact, mathematically precise characteristics of your hearing loss, but to you it may as well be written in Greek.
The audiogram creates confusion and complication 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 puzzling doesn’t mean that it’s hard to interpret.
After reading through this article, and with a little vocabulary and a handful of basic principles, you’ll be reading audiograms like a expert, so that you can focus on what actually is important: better hearing.
Some advice: as you read the article, reference the above blank audiogram. This will make it much easier to comprehend, and we’ll address all of those cryptic marks the hearing instrument specialist adds later.
Understanding Sound Frequencies and Decibels
The audiogram is essentially 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, weak sound. As you go down the line, the decibel levels increase, representing steadily 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 proceed along the horizontal axis to the right, the frequency will gradually increase until it gets to 8,000 Hz. Vowel sounds of speech are commonly 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 sketch a diagonal line to the bottom right corner, you would be increasing the frequency of sound (progressing from vowel sounds to consonant sounds) while increasing the volume of sound (moving from softer to louder volume).
Testing Hearing and Marking Up the Audiogram
So, what’s with all the marks you usually see on this basic graph?
Simple. Start at the top left corner of the graph, at the lowest frequency (125 Hz). Your hearing instrument specialist will present you with a sound at this frequency via earphones, beginning with the lowest volume decibel level. If you can hear it at the lowest level (0 decibels), a mark is created at the joining of 125 Hz and 0 decibels. If you are not able to perceive the 125 Hz sound at 0 decibels, the sound will be presented for a second time at the next loudest decibel level (10 decibels). If you can perceive it at 10 decibels, a mark is created. If not, continue on to 15 decibels, and so on.
This exact routine is duplicated for every frequency as the hearing instrument specialist proceeds along the horizontal frequency axis. A mark is created at the lowest perceivable decibel level you can hear for each sound frequency.
As for 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 most often applied to mark the points for the left ear; an O is applied for the right ear. You may discover some other symbols, but these are less important for your basic understanding.
What Normal Hearing Looks Like
So what is thought to be 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 all the way across. Any mark made beneath this line may display hearing loss. If you can hear all frequencies underneath this line (25 decibels or higher), then you most likely have normal hearing.
If, on the other hand, you cannot perceive the sound of a certain frequency at 0-25 dB, you probably have some kind of hearing loss. The smallest decibel level at which you can perceive sound at that frequency determines the tier of your hearing loss.
To provide an example, consider the 1,000 Hertz frequency. If you can perceive this frequency at 0-25 decibels, you have normal hearing for this frequency. If the minimum decibel level at which you can hear this frequency is 40 decibels, for instance, then you have moderate hearing loss at this frequency.
As a summary, here are the decibel levels associated 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 might an audiogram with signals of hearing loss look like? Because many 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 graph slanting downward horizontally to the right.
This indicates that at the higher-frequencies, it takes a progressively louder decibel level for you to perceive the sound. Furthermore, seeing that higher-frequency sounds are connected with the consonant sounds of speech, high-frequency hearing loss damages your ability to grasp and pay attention to conversations.
There are some other, less frequent patterns of hearing loss that can appear on the audiogram, but that’s probably too much detail for this entry.
Testing Your New-Found Knowledge
You now know the essentials of how to interpret an audiogram. So go ahead, arrange that hearing test and surprise your hearing instrument specialist with your newfound talents. And just imagine the look on their face when you tell them all about your high frequency hearing loss before they even say a word.