You have 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 reveal to you 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 complication at a time when you’re supposed to be focusing on how to strengthen your hearing. But don’t let it trick you — just because the audiogram looks puzzling 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 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 marks the hearing specialist adds later on.
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 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, representing progressively 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 gradually increase until it hits 8,000 Hz. Vowel sounds of speech are in general 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 increasing the frequency of sound (switching from vowel sounds to consonant sounds) while increasing the volume of sound (moving from fainter to louder volume).
Examining Hearing and Marking Up the Audiogram
So, what’s with all the marks you normally see on this basic chart?
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 headphones, beginning with the smallest volume decibel level. If you can perceive 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 hear the 125 Hz sound at 0 decibels, the sound will be presented once more at the next loudest decibel level (10 decibels). If you can hear it at 10 decibels, a mark is created. If not, proceed on to 15 decibels, and so on.
This equivalent technique is carried out 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 perceive 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 regularly applied to mark the points for the left ear; an O is used for the right ear. You may notice some additional characters, but these are less significant for your basic understanding.
What Normal Hearing Looks Like
So what is considered normal hearing, and what would that look like on the audiogram?
People with regular hearing should be able to perceive every sound frequency level (125 to 8000 Hz) at 0-25 decibels. What might this look like on the audiogram?
Just take the blank graph, find 25 decibels on the vertical axis, and draw a horizontal line completely across. Any mark made under this line may reveal hearing loss. If you can hear all frequencies under this line (25 decibels or higher), then you probably have normal hearing.
If, however, you cannot perceive the sound of a specific frequency at 0-25 dB, you very likely have some form of hearing loss. The smallest decibel level at which you can perceive sound at that frequency establishes the amount of your hearing loss.
For 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 smallest 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 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 marks of hearing loss look like? Since 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 downward sloping line from the top left corner of the chart sloping downward horizontally to the right.
This signifies that at the higher-frequencies, it takes a increasingly louder decibel level for you to perceive the sound. And, seeing as higher-frequency sounds are connected with the consonant sounds of speech, high-frequency hearing loss weakens your ability to understand and follow conversations.
There are a few other, less frequent patterns of hearing loss that can appear on the audiogram, but that’s probably too much information for this entry.
Test Your New Knowledge
You now know the fundamentals of how to read an audiogram. So go ahead, book 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.