You have just finished your hearing test. The hearing specialist is now entering the room and provides 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 properties of your hearing loss, but to you it might 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 enhance your hearing. But don’t let it deceive you — just because the audiogram looks complex doesn’t mean that it’s hard to interpret.
After reading this article, and with a little terminology and a few basic concepts, you’ll be reading audiograms like a seasoned professional, so that you can concentrate on what actually is important: 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 on.
Understanding Sound Frequencies and Decibels
The audiogram is essentially just a graph 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 elementary 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, representing progressively louder sounds until you get to 100 dB.
The horizontal axis records sound frequency, measured in Hertz (Hz). Beginning 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 progressively increase until it hits 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 start 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 increasing the intensity of sound (moving from softer to louder volume).
Evaluating Hearing and Marking Up the Audiogram
So, what’s with all the markings you normally see on this simple graph?
Simple. Begin 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, starting with the lowest volume decibel level. If you can hear it at the lowest level (0 decibels), a mark is made at the intersection point 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 perceive it at 10 decibels, a mark is made. If not, continue on to 15 decibels, and so on.
This same technique is duplicated for each frequency as the hearing specialist proceeds along the horizontal frequency line. A mark is made at the lowest perceivable decibel level you can perceive for each sound frequency.
As for the other symbols? If you see 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 applied for the right ear. You may see some additional symbols, but these are less crucial for your basic understanding.
What Normal Hearing Looks Like
So what is considered 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 would this look like on the audiogram?
Take the blank graph, locate 25 decibels on the vertical axis, and sketch a horizontal line all the way across. Any mark made below this line may signal 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 can’t perceive the sound of a specific frequency at 0-25 dB, you likely have some type of hearing loss. The lowest decibel level at which you can perceive sound at that frequency pinpoints the level of your hearing loss.
By way of example, 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 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 a summary, here are the decibel levels identified with normal hearing along with the levels identified 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 indicators 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 downwards sloping line from the top left corner of the chart sloping downward horizontally to the right.
This will mean that at the higher-frequencies, it requires a increasingly louder decibel level for you to perceive the sound. Furthermore, considering that higher-frequency sounds are linked 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 prevalent patterns of hearing loss that can show up on the audiogram, but that’s probably too much detail for this entry.
Testing Your New Knowledge
You now know the basics of how to interpret an audiogram. So go ahead, schedule that hearing test and impress 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.