You have 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 signs, colors, and lines. This is supposed to demonstrate to you the exact, mathematically precise attributes of your hearing loss, but to you it may as well be written in Greek.
The audiogram adds confusion and complexity at a time when you’re supposed to be focusing on how to enhance your hearing. But don’t let it mislead you — just because the audiogram looks confusing doesn’t mean that it’s difficult to interpret.
After reading this article, and with a little terminology and a handful of basic principles, you’ll be reading audiograms like a expert, so that you can focus on what really counts: healthier hearing.
Some advice: as you read the article, reference the above blank audiogram. This will make it easier to understand, and we’ll cover all of those cryptic markings the hearing specialist adds later.
Understanding Sound Frequencies and Decibels
The audiogram is basically 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, standing for 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 move over along the horizontal axis to the right, the frequency will gradually increase until it hits 8,000 Hz. Vowel sounds of speech are generally 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 raising the frequency of sound (progressing from vowel sounds to consonant sounds) while increasing the level of sound (moving from softer to louder volume).
Evaluating Hearing and Marking Up the Audiogram
So, what’s with all the marks you normally see on this basic chart?
Simple. Start at the top left corner of the graph, at the lowest frequency (125 Hz). Your hearing consultant will present you with a sound at this frequency through headphones, beginning with the smallest volume decibel level. If you can perceive it at the lowest level (0 decibels), a mark is created at the intersection point of 125 Hz and 0 decibels. If you can’t perceive 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 perceive it at 10 decibels, a mark is created. If not, advance on to 15 decibels, and so on.
This exact technique is duplicated for every frequency as the hearing specialist moves along the horizontal frequency line. A mark is produced at the lowest perceivable decibel level you can hear for each individual sound frequency.
In terms of the other symbols? If you see 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 as a rule used to mark the points for the left ear; an O is applied for the right ear. You may see some other characters, but these are less important for your basic understanding.
What Normal Hearing Looks Like
So what is judged 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?
Just take the blank graph, find 25 decibels on the vertical axis, and draw a horizontal line completely across. Any mark made below this line may demonstrate hearing loss. If you can perceive all frequencies beneath this line (25 decibels or higher), then you most likely have normal hearing.
If, on the other hand, you can’t perceive the sound of a specific frequency at 0-25 dB, you probably have some type of hearing loss. The lowest decibel level at which you can perceive sound at that frequency determines the tier 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 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 associated with normal hearing along with the levels connected 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 indications of hearing loss look like? Seeing that 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 downward slanting 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 progressively louder decibel level for you to experience the sound. Furthermore, considering that higher-frequency sounds are connected with the consonant sounds of speech, high-frequency hearing loss damages your ability to understand and pay attention to conversations.
There are a few other, less frequent patterns of hearing loss that can manifest on the audiogram, but that’s probably too much information for this entry.
Testing Your New-Found Knowledge
You now know the essentials of how to read an audiogram. So go ahead, schedule that hearing test and surprise 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.