Audiogram

You’ve just completed your hearing test. The hearing specialist is now entering the room and provides you with a chart, like the one above, except that it has all of these characters, colors, and lines. This is intended to highlight to you the exact, mathematically precise characteristics of your hearing loss, but to you it might as well be written in Greek.

The audiogram adds confusion and complication at a time when you’re supposed to be focusing on how to strengthen your hearing. But don’t let it fool you — just because the audiogram looks complicated doesn’t mean that it’s hard to interpret.

After going over this article, and with a little terminology and a few basic principles, you’ll be reading audiograms like a expert, so that you can focus on what actually matters: 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 graph 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 fundamental 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 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 continue along the horizontal axis to the right, the frequency will steadily 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 start off 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 (progressing from vowel sounds to consonant sounds) while increasing the level of sound (moving from softer to louder volume).

Examining Hearing and Marking Up the Audiogram

So, what’s with all the markings you usually see on this simple chart?

Easy. Start 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 headsets, starting with the smallest volume decibel level. If you can perceive it at the lowest level (0 decibels), a mark is made 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 provided 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 same procedure is reiterated for every frequency as the hearing specialist progresses along the horizontal frequency axis. A mark is made at the lowest perceivable decibel level you can hear for every 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 normally 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 critical 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 healthy 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?

Just take the empty graph, find 25 decibels on the vertical axis, and sketch a horizontal line all the way across. Any mark made below this line may suggest 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 cannot perceive the sound of a specific frequency at 0-25 dB, you likely have some form of hearing loss. The smallest decibel level at which you can perceive sound at that frequency pinpoints the extent of your hearing loss.

For example, take the 1,000 Hertz frequency. If you can perceive this frequency at 0-25 decibels, you have normal hearing for this frequency. If the smallest decibel level at which you can perceive 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 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 indications of hearing loss look like? Considering that the majority of cases of hearing loss are in the higher frequencies (referred to as — you guessed it — high-frequency hearing loss), the audiogram would have a descending slanting line from the top left corner of the chart sloping downward horizontally to the right.

This will mean that at the higher-frequencies, it takes a increasingly 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 impairs your ability to comprehend and follow conversations.

There are a few other, less frequent patterns of hearing loss that can show up on the audiogram, but that’s probably too much detail for this entry.

Testing Your New Knowledge

You now know the essentials of how to read an audiogram. So go ahead, book 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.