You’ve just concluded your hearing test. The hearing specialist is now entering the room and presents you with a graph, like the one above, except that it has all of these icons, colors, and lines. This is supposed to reveal to you the exact, mathematically precise characteristics of your hearing loss, but to you it may as well be written in Greek.
The audiogram adds 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 hard to understand.
After reading through this article, and with a little terminology and a few basic concepts, you’ll be reading audiograms like a expert, so that you can concentrate on what really is important: better hearing.
Some advice: as you read the article, reference the above blank audiogram. This will make it much easier to understand, and we’ll cover all of those cryptic marks the hearing specialist adds later on.
Understanding Sound Frequencies and Decibels
The audiogram is essentially 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 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, weak sound. As you move down the line, the decibel levels increase, representing 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 gradually increase until it arrives at 8,000 Hz. Vowel sounds of speech are in general low frequency sounds, while consonant sounds of speech are high frequency sounds.
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 (progressing from vowel sounds to consonant sounds) while increasing the strength 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 basic graph?
Easy. 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 through headphones, starting with the smallest volume decibel level. If you can hear it at the lowest level (0 decibels), a mark is created 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 presented for a second time 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 process is repeated for every frequency as the hearing specialist proceeds along the horizontal frequency line. A mark is made at the lowest perceivable decibel level you can perceive for each 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 regularly used to mark the points for the left ear; an O is employed for the right ear. You may discover some other symbols, but these are less significant for your basic understanding.
What Normal Hearing Looks Like
So what is deemed as normal hearing, and what would that look like on the audiogram?
Individuals with normal hearing should be able to perceive every sound frequency level (125 to 8000 Hz) at 0-25 decibels. What would this look like on the audiogram?
Take the blank graph, find 25 decibels on the vertical axis, and draw a horizontal line all the way across. Any mark made below this line may signify hearing loss. If you can perceive all frequencies under this line (25 decibels or higher), then you probably have normal hearing.
If, however, you cannot perceive the sound of a particular 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 amount of your hearing loss.
For instance, 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 minimum decibel level at which you can perceive this frequency is 40 decibels, for example, then you have moderate hearing loss at this frequency.
As a summary, here are the decibel levels associated with normal hearing along with the levels linked 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 signals of hearing loss look like? Because 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 slanting line from the top left corner of the graph sloping downward horizontally to the right.
This indicates that at the higher-frequencies, it takes a increasingly louder decibel level for you to experience 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 follow conversations.
There are a few other, less prevalent patterns of hearing loss that can show up on the audiogram, but that’s probably too much detail for this entry.
Testing Your New-Found Knowledge
You now know the fundamentals of how to read an audiogram. So go ahead, arrange that hearing test and surprise your hearing specialist with your newfound abilities. 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.