You’ve just concluded your hearing test. The hearing specialist is now entering 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 highlight 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 complication 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 puzzling doesn’t mean that it’s difficult to grasp.
After looking through this article, and with a little terminology and a few basic concepts, you’ll be reading audiograms like a professional, so that you can focus on what really is important: healthier 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 markings the hearing specialist adds later on.
Understanding Sound Frequencies and Decibels
The audiogram is basically just a graph 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 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 go 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 proceed along the horizontal axis to the right, the frequency will steadily increase until it reaches 8,000 Hz. Vowel sounds of speech are commonly low frequency sounds, while consonant sounds of speech are high frequency sounds.
And 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 (shifting from vowel sounds to consonant sounds) while raising the strength of sound (moving from softer to louder volume).
Examining 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 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 made at the intersection 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 perceive it at 10 decibels, a mark is made. If not, move on to 15 decibels, and so on.
This equivalent process is reiterated for every frequency as the hearing specialist progresses along the horizontal frequency line. 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 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 commonly used to mark the points for the left ear; an O is applied for the right ear. You may discover some other characters, but these are less vital for your basic understanding.
What Normal Hearing Looks Like
So what is judged to be normal hearing, and what would that look like on the audiogram?
People with standard 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, locate 25 decibels on the vertical axis, and draw a horizontal line completely across. Any mark made underneath this line may indicate hearing loss. If you can hear all frequencies underneath this line (25 decibels or higher), then you very likely have normal hearing.
If, however, you can’t perceive the sound of a certain 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 grade of your hearing loss.
For instance, 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 smallest decibel level at which you can hear this frequency is 40 decibels, for instance, then you have moderate hearing loss at this frequency.
As an overview, here are the decibel levels connected 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 would an audiogram with signals of hearing loss look like? Since the majority of instances 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 chart slanting downward horizontally to the right.
This will mean that at the higher-frequencies, it takes a increasingly louder decibel level for you to perceive the sound. And, seeing that higher-frequency sounds are associated with the consonant sounds of speech, high-frequency hearing loss weakens your ability to comprehend and follow conversations.
There are some other, less prevalent patterns of hearing loss that can appear on the audiogram, but that’s probably too much information for this article.
Test Your New-Found Knowledge
You now know the basics of how to interpret an audiogram. So go ahead, schedule 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.