You’ve just completed your hearing test. The hearing specialist is now coming into the room and presents you with a chart, like the one above, except that it has all of these characters, colors, and lines. This is intended to provide you with the exact, mathematically precise characteristics 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 improve your hearing. But don’t let it mislead you — just because the audiogram looks perplexing doesn’t mean that it’s hard to grasp.
After looking through this article, and with a little terminology and a handful of basic concepts, you’ll be reading audiograms like a professional, so that you can focus on what actually is important: 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 address all of those cryptic markings the hearing specialist adds later.
Understanding Sound Frequencies and Decibels
The audiogram is essentially 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 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, faint sound. As you go down the line, the decibel levels increase, standing for gradually 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 arrives at 8,000 Hz. Vowel sounds of speech are normally 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 draw a diagonal line to the bottom right corner, you would be raising the frequency of sound (switching from vowel sounds to consonant sounds) while raising the volume of sound (moving from fainter to louder volume).
Examining Hearing and Marking Up the Audiogram
So, what’s with all the markings you normally see on this simple graph?
Easy. Start 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 by means of headsets, starting 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 presented 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 exact routine is duplicated for every frequency as the hearing specialist moves along the horizontal frequency line. A mark is created at the lowest perceivable decibel level you can perceive for every different sound frequency.
In terms of the other symbols? If you observe 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 employed for the right ear. You may notice some other symbols, but these are less relevant 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 standard 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 blank graph, locate 25 decibels on the vertical axis, and draw a horizontal line completely across. Any mark made underneath this line may signify 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 very likely have some type of hearing loss. The lowest decibel level at which you can perceive sound at that frequency defines the grade of your hearing loss.
By way of example, consider the 1,000 Hertz frequency. If you can perceive 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 example, 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 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? Seeing as 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 descending sloping line from the top left corner of the chart sloping downward horizontally to the right.
This indicates that at the higher-frequencies, it takes a progressively louder decibel level for you to perceive the sound. And, since higher-frequency sounds are connected with the consonant sounds of speech, high-frequency hearing loss damages your ability to grasp and pay attention to 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 entry.
Testing Your New Knowledge
You now know the basics of how to interpret an audiogram. So go ahead, arrange that hearing test and surprise 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.