You have just finished your hearing test. The hearing specialist is now entering the room and presents you with a chart, like the one above, except that it has all of these icons, colors, and lines. This is intended to present to you the exact, mathematically precise attributes of your hearing loss, but to you it might as well be written in Greek.
The audiogram adds confusion and complication at a time when you’re supposed to be concentrating on how to strengthen your hearing. But don’t let it fool you — just because the audiogram looks perplexing doesn’t mean that it’s difficult to grasp.
After looking through this article, and with a little vocabulary and a handful of basic concepts, you’ll be reading audiograms like a professional, so that you can concentrate 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 cover all of those cryptic marks the hearing specialist adds later on.
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, faint sound. As you move down the line, the decibel levels increase, standing for 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 continue along the horizontal axis to the right, the frequency will progressively increase until it reaches 8,000 Hz. Vowel sounds of speech are in general low frequency sounds, while consonant sounds of speech are high frequency sounds.
And so, if you were to start off 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 raising the level of sound (moving from softer to louder volume).
Evaluating Hearing and Marking Up the Audiogram
So, what’s with all the marks you usually see on this basic graph?
Easy. Begin at the top left corner of the graph, at the lowest frequency (125 Hz). Your hearing consultant 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 intersection of 125 Hz and 0 decibels. If you are not able to hear the 125 Hz sound at 0 decibels, the sound will be presented once again 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 technique is repeated for each frequency as the hearing specialist progresses along the horizontal frequency line. A mark is made at the lowest perceivable decibel level you can perceive for each individual 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 ordinarily applied to mark the points for the left ear; an O is used for the right ear. You may observe some additional symbols, but these are less significant 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?
People with regular 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 empty graph, find 25 decibels on the vertical axis, and sketch a horizontal line all the way across. Any mark made below this line may signify hearing loss. If you can hear all frequencies beneath this line (25 decibels or higher), then you likely have normal hearing.
If, on the other hand, you cannot 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 defines the grade of your hearing loss.
For instance, 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 example, 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? Given that many cases of hearing loss are in the higher frequencies (referred to as — you guessed it — high-frequency hearing loss), the audiogram would have a descending sloping line from the top left corner of the chart slanting downward horizontally to the right.
This indicates that at the higher-frequencies, it requires a increasingly 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 impairs your ability to comprehend and pay attention to conversations.
There are other, less typical patterns of hearing loss that can appear on the audiogram, but that’s probably too much information for this article.
Test Your New Knowledge
You now know the basics of how to interpret an audiogram. So go ahead, schedule that hearing test and surprise your hearing specialist with your newfound abilities. 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.