You have just completed your hearing test. The hearing specialist is now entering the room and presents you with a graph, like the one above, except that it has all of these icons, colors, and lines. This is designed to explain to you the exact, mathematically precise features of your hearing loss, but to you it may as well be written in Greek.
The audiogram adds 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 fool you — just because the audiogram looks confusing doesn’t mean that it’s difficult to grasp.
After looking through this article, and with a little vocabulary and a handful of basic principles, you’ll be reading audiograms like a professional, so that you can concentrate on what really matters: 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 cover 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 fundamental level it’s just a chart graphing two variables, as follows:
The vertical axis records 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, 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 move along the horizontal axis to the right, the frequency will gradually increase until it hits 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 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 (progressing from vowel sounds to consonant sounds) while raising the strength of sound (moving from fainter 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. Begin 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 via headphones, starting with the smallest volume decibel level. If you can hear it at the lowest level (0 decibels), a mark is made at the convergence 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 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, proceed on to 15 decibels, and so on.
This equivalent routine is repeated for every frequency as the hearing specialist travels along the horizontal frequency line. A mark is produced at the lowest perceivable decibel level you can perceive for each individual sound frequency.
Regarding 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 usually applied to mark the points for the left ear; an O is employed for the right ear. You may notice some other symbols, but these are less significant 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 normal 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?
Take the empty graph, find 25 decibels on the vertical axis, and draw a horizontal line completely across. Any mark made below this line may suggest hearing loss. If you can hear all frequencies under this line (25 decibels or higher), then you very likely have normal hearing.
If, on the other hand, you cannot perceive the sound of a certain frequency at 0-25 dB, you very likely have some type of hearing loss. The lowest decibel level at which you can perceive sound at that frequency establishes the grade of your hearing loss.
As an illustration, consider the 1,000 Hertz frequency. If you can hear 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 an overview, here are the decibel levels linked 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? Since the majority of cases of hearing loss are in the higher frequencies (referred to as — you guessed it — high-frequency hearing loss), the audiogram would have a downward slanting line from the top left corner of the chart sloping downward horizontally to the right.
This signifies that at the higher-frequencies, it takes a progressively louder decibel level for you to perceive the sound. Furthermore, given that higher-frequency sounds are associated with the consonant sounds of speech, high-frequency hearing loss impairs your ability to understand and follow conversations.
There are some other, less prevalent patterns of hearing loss that can turn up on the audiogram, but that’s probably too much detail for this entry.
Test Your New Knowledge
You now know the nuts and bolts of how to read an audiogram. So go ahead, schedule that hearing test and surprise your hearing 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.