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 symbols, colors, and lines. This is supposed to provide you with the exact, mathematically precise features 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 focusing on how to strengthen your hearing. But don’t let it mislead you — just because the audiogram looks complicated doesn’t mean that it’s difficult to understand.
After looking through this article, and with a little terminology and a handful of basic concepts, you’ll be reading audiograms like a expert, so that you can focus on what really is important: better hearing.
Some advice: as you read the article, reference the above blank audiogram. This will make it much easier to understand, and we’ll address all of those cryptic marks the hearing specialist adds later on.
Understanding Sound Frequencies and Decibels
The audiogram is basically 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 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 go down the line, the decibel levels increase, standing for increasingly 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 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 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 raising the volume 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 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, beginning with the smallest volume decibel level. If you can perceive 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 hear the 125 Hz sound at 0 decibels, the sound will be presented once more at the next loudest decibel level (10 decibels). If you can hear it at 10 decibels, a mark is made. If not, advance on to 15 decibels, and so on.
This exact method is carried out 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 hear for every different sound frequency.
In terms of 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 used to mark the points for the left ear; an O is applied for the right ear. You may notice some additional characters, 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 might this look like on the audiogram?
Take the blank graph, find 25 decibels on the vertical axis, and sketch a horizontal line completely across. Any mark made below this line may suggest hearing loss. If you can perceive all frequencies under 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 specific frequency at 0-25 dB, you very likely have some form of hearing loss. The lowest decibel level at which you can perceive sound at that frequency determines the extent of your hearing loss.
To provide an example, take 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 perceive this frequency is 40 decibels, for instance, then you have moderate hearing loss at this frequency.
As a summary, here are the decibel levels linked 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 indicators of hearing loss look like? Because 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 graph sloping downward horizontally to the right.
This will mean that at the higher-frequencies, it requires a progressively louder decibel level for you to experience the sound. Furthermore, seeing that higher-frequency sounds are associated with the consonant sounds of speech, high-frequency hearing loss damages your ability to grasp and follow conversations.
There are a few other, less prevalent patterns of hearing loss that can show up on the audiogram, but that’s probably too much detail for this entry.
Test Your New Knowledge
You now know the essentials of how to read an audiogram. So go ahead, arrange that hearing test and impress 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.