You have just concluded your hearing test. The hearing specialist is now coming into the room and provides you with a graph, like the one above, except that it has all of these signs, colors, and lines. This is intended to explain to you the exact, mathematically precise characteristics of your hearing loss, but to you it might as well be written in Greek.
The audiogram contributes confusion and complication at a time when you’re supposed to be focusing on how to improve your hearing. But don’t let it deceive you — just because the audiogram looks perplexing doesn’t mean that it’s difficult to understand.
After going over this article, and with a little terminology and a handful of basic concepts, you’ll be reading audiograms like a professional, so that you can concentrate on what really matters: healthier 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 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 fundamental 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 go 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 steadily increase until it hits 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 begin 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 (going from vowel sounds to consonant sounds) while increasing the intensity of sound (moving from fainter to louder volume).
Testing Hearing and Marking Up the Audiogram
So, what’s with all the marks 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 professional will present you with a sound at this frequency via headsets, beginning with the smallest volume decibel level. If you can perceive it at the lowest level (0 decibels), a mark is created 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 process is repeated for every frequency as the hearing specialist travels along the horizontal frequency line. A mark is created 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 generally used to mark the points for the left ear; an O is applied for the right ear. You may observe some other symbols, but these are less significant for your basic understanding.
What Normal Hearing Looks Like
So what is regarded as normal hearing, and what would that look like on the audiogram?
People with normal hearing should be able to perceive every sound frequency level (125 to 8000 Hz) at 0-25 decibels. What would this look like on the audiogram?
Just take the blank graph, find 25 decibels on the vertical axis, and sketch a horizontal line completely across. Any mark made underneath this line may display hearing loss. If you can perceive all frequencies under 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 likely have some kind 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, 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 lowest decibel level at which you can hear this frequency is 40 decibels, for example, 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 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 indicators of hearing loss look like? As many cases of hearing loss are in the higher frequencies (labeled as — you guessed it — high-frequency hearing loss), the audiogram would have a downward sloping line from the top left corner of the chart sloping downward horizontally to the right.
This signifies that at the higher-frequencies, it requires a progressively louder decibel level for you to experience the sound. And, seeing that higher-frequency sounds are associated with the consonant sounds of speech, high-frequency hearing loss weakens your ability to grasp and pay attention to conversations.
There are other, less frequent 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 surprise your hearing specialist with your newfound abilities. And just think about the look on their face when you tell them all about your high frequency hearing loss before they even say a word.