You have just concluded your hearing test. The hearing specialist is now coming into the room and presents you with a chart, like the one above, except that it has all of these signs, colors, and lines. This is designed to demonstrate to you the exact, mathematically precise properties of your hearing loss, but to you it may as well be written in Greek.
The audiogram contributes confusion and complexity at a time when you’re supposed to be focusing on how to enhance 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 reading through this article, and with a little vocabulary and a few basic concepts, you’ll be reading audiograms like a seasoned professional, so that you can focus on what really counts: 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 tackle all of those cryptic markings the hearing specialist adds later.
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, faint 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 proceed along the horizontal axis to the right, the frequency will steadily increase until it gets to 8,000 Hz. Vowel sounds of speech are typically low frequency sounds, while consonant sounds of speech are high frequency sounds.
So, if you were to start 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 (switching from vowel sounds to consonant sounds) while increasing the level of sound (moving from fainter to louder volume).
Testing Hearing and Marking Up the Audiogram
So, what’s with all the markings you normally see on this simple graph?
Simple. Start off 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, starting with the smallest volume decibel level. If you can hear it at the lowest level (0 decibels), a mark is created at the junction of 125 Hz and 0 decibels. If you can’t perceive the 125 Hz sound at 0 decibels, the sound will be provided again at the next loudest decibel level (10 decibels). If you can hear it at 10 decibels, a mark is made. If not, continue on to 15 decibels, and so on.
This equivalent procedure is done again for each frequency as the hearing specialist moves along the horizontal frequency axis. A mark is produced at the lowest perceivable decibel level you can perceive for each sound frequency.
In terms of 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 generally used to mark the points for the left ear; an O is used for the right ear. You may discover some other characters, but these are less critical for your basic understanding.
What Normal Hearing Looks Like
So what is considered to be normal hearing, and what would that look like on the audiogram?
Individuals with regular hearing should be able to perceive every sound frequency level (125 to 8000 Hz) at 0-25 decibels. What might this look like on the audiogram?
Just take the empty graph, locate 25 decibels on the vertical axis, and sketch a horizontal line completely across. Any mark made underneath this line may indicate hearing loss. If you can hear all frequencies below this line (25 decibels or higher), then you most likely have normal hearing.
If, on the other hand, you can’t perceive the sound of a specified frequency at 0-25 dB, you likely have some type of hearing loss. The smallest decibel level at which you can perceive sound at that frequency establishes the tier of your hearing loss.
As 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 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 a summary, here are the decibel levels connected 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 might an audiogram with indications of hearing loss look like? Seeing that 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 downwards sloping line from the top left corner of the graph slanting downward horizontally to the right.
This signifies that at the higher-frequencies, it takes a increasingly louder decibel level for you to perceive the sound. And, since higher-frequency sounds are linked with the consonant sounds of speech, high-frequency hearing loss weakens your ability to comprehend and follow conversations.
There are a few other, less common patterns of hearing loss that can appear on the audiogram, but that’s probably too much detail for this article.
Testing Your New Knowledge
You now know the basics of how to read an audiogram. So go ahead, book 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.