You’ve just concluded 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 symbols, colors, and lines. This is intended to show you the exact, mathematically precise attributes of your hearing loss, but to you it may 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 trick you — just because the audiogram looks perplexing doesn’t mean that it’s difficult to interpret.
After reading this article, and with a little vocabulary and a few basic concepts, you’ll be reading audiograms like a professional, so that you can focus on what actually matters: 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 cover all of those cryptic marks the hearing specialist adds later on.
Understanding Sound Frequencies and Decibels
The audiogram is essentially 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 move down the line, the decibel levels increase, standing for 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 continue along the horizontal axis to the right, the frequency will steadily increase until it gets to 8,000 Hz. Vowel sounds of speech are usually low frequency sounds, while consonant sounds of speech are high frequency sounds.
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 raising the frequency of sound (switching from vowel sounds to consonant sounds) while increasing the intensity of sound (moving from softer to louder volume).
Assessing Hearing and Marking Up the Audiogram
So, what’s with all the markings you normally see on this simple chart?
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 by way of headphones, beginning with the lowest volume decibel level. If you can hear it at the lowest level (0 decibels), a mark is made at the convergence of 125 Hz and 0 decibels. If you are not able to hear the 125 Hz sound at 0 decibels, the sound will be provided once again at the next loudest decibel level (10 decibels). If you can hear it at 10 decibels, a mark is made. If not, move on to 15 decibels, and so on.
This identical method is carried out 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 hear for every 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 almost always applied to mark the points for the left ear; an O is applied for the right ear. You may see some additional characters, but these are less essential for your basic understanding.
What Normal Hearing Looks Like
So what is seen as normal hearing, and what would that look like on the audiogram?
Individuals with normal 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 empty graph, find 25 decibels on the vertical axis, and sketch a horizontal line entirely across. Any mark made below this line may demonstrate hearing loss. If you can perceive all frequencies beneath 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 probably have some kind of hearing loss. The smallest decibel level at which you can perceive sound at that frequency establishes the tier 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 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 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 marks of hearing loss look like? Given that the majority of instances of hearing loss are in the higher frequencies (labeled as — you guessed it — high-frequency hearing loss), the audiogram would have a downwards slanting line from the top left corner of the chart slanting downward horizontally to the right.
This signifies that at the higher-frequencies, it takes a progressively louder decibel level for you to experience the sound. Furthermore, considering that higher-frequency sounds are linked with the consonant sounds of speech, high-frequency hearing loss damages your ability to comprehend and follow conversations.
There are a few other, less prevalent patterns of hearing loss that can turn up on the audiogram, but that’s probably too much detail for this article.
Testing Your New-Found Knowledge
You now know the basics of how to read an audiogram. So go ahead, schedule that hearing test and impress 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.