You have just finished 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 properties of your hearing loss, but to you it may as well be written in Greek.
The audiogram creates 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 perplexing doesn’t mean that it’s hard to understand.
After reading 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 actually counts: better hearing.
Some advice: as you read the article, reference the above blank audiogram. This will make it much easier to comprehend, and we’ll tackle all of those cryptic marks the hearing specialist adds later.
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 basic 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, representing 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 proceed along the horizontal axis to the right, the frequency will steadily increase until it gets to 8,000 Hz. Vowel sounds of speech are typically low frequency sounds, while consonant sounds of speech are high frequency sounds.
So, if you were to begin 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 (progressing 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 markings you usually see on this basic graph?
Easy. Begin at the top left corner of the graph, at the lowest frequency (125 Hz). Your hearing specialist will present you with a sound at this frequency through headsets, starting with the smallest 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 can’t 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 exact routine is carried out for each frequency as the hearing specialist progresses 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 typically used to mark the points for the left ear; an O is employed for the right ear. You may see some additional symbols, but these are less critical 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 might this look like on the audiogram?
Just take the empty graph, find 25 decibels on the vertical axis, and sketch a horizontal line completely across. Any mark made under this line may display hearing loss. If you can perceive all frequencies beneath this line (25 decibels or higher), then you probably have normal hearing.
If, on the other hand, you can’t perceive the sound of a particular 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 defines the grade of your hearing loss.
By way of 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 connected 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 might an audiogram with signs 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 downwards slanting line from the top left corner of the graph sloping downward horizontally to the right.
This means that at the higher-frequencies, it requires a increasingly louder decibel level for you to perceive the sound. And, considering that higher-frequency sounds are connected with the consonant sounds of speech, high-frequency hearing loss impairs your ability to comprehend and follow conversations.
There are some other, less typical 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 nuts and bolts of how to interpret an audiogram. So go ahead, arrange that hearing test and surprise your hearing specialist with your newfound abilities. 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.