You’ve just finalized your hearing test. The hearing specialist is now entering the room and presents you with a graph, like the one above, except that it has all of these characters, colors, and lines. This is designed to provide you with the exact, mathematically precise features 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 concentrating on how to strengthen your hearing. But don’t let it fool you — just because the audiogram looks confusing doesn’t mean that it’s hard to grasp.
After reading this article, and with a little terminology and a few basic principles, you’ll be reading audiograms like a pro, so that you can focus on what actually matters: healthier hearing.
Some advice: as you read the article, reference the above blank audiogram. This will make it much easier to comprehend, and we’ll cover all of those cryptic marks 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, weak sound. As you move 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). Starting 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 gets to 8,000 Hz. Vowel sounds of speech are usually low frequency sounds, while consonant sounds of speech are high frequency sounds.
And 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 increasing the frequency of sound (moving from vowel sounds to consonant sounds) while increasing the volume of sound (moving from softer to louder volume).
Assessing Hearing and Marking Up the Audiogram
So, what’s with all the markings you usually 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 through earphones, starting with the lowest volume decibel level. If you can hear it at the lowest level (0 decibels), a mark is made at the joining of 125 Hz and 0 decibels. If you are not able to perceive the 125 Hz sound at 0 decibels, the sound will be presented again at the next loudest decibel level (10 decibels). If you can perceive it at 10 decibels, a mark is created. If not, move on to 15 decibels, and so on.
This equivalent process is reiterated for each frequency as the hearing specialist proceeds along the horizontal frequency line. A mark is produced 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 most often used to mark the points for the left ear; an O is used for the right ear. You may discover some other symbols, but these are less crucial 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?
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 blank graph, find 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 beneath this line (25 decibels or higher), then you more than 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 determines the stage 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 minimum decibel level at which you can hear this frequency is 40 decibels, for example, then you have moderate hearing loss at this frequency.
As an overview, here are the decibel levels correlated with normal hearing along with the levels correlated 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 marks of hearing loss look like? Considering that the majority of cases of hearing loss are in the higher frequencies (labeled 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 takes a increasingly louder decibel level for you to experience the sound. Furthermore, considering that higher-frequency sounds are associated with the consonant sounds of speech, high-frequency hearing loss weakens your ability to understand and pay attention to conversations.
There are a few other, less frequent 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, schedule that hearing test and impress your hearing specialist with your newfound talents. 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.