Audiogram
How to Understand an Audiogram
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The X-axis (horizontal) is used to display sound frequency.
- The usual frequency range of sounds is between 250 Hz (low-pitched sounds) and 8000 Hz (high-pitched sounds).
- Sound frequency is the rate at which a sound wave vibrates, and is directly linked to our sensation of sound pitch.
- The vibrations of low-frequency sounds, like a bass drum, are slower than those of high-frequency noises like birds tweeting.
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The Y-axis (vertical) represents sound intensity levels.
- Sound intensity illustrates how loud a sound is, and is measured in decibels (dB).
- The frequency range is -10 dB HL (delicate sounds, like a whisper) to 120 dB HL (very loud sounds, like a music performance).
Symbols on Audiograms
Symbols that appear most frequently on an audiogram graph are:
| SYMBOL | MEANING |
|---|---|
| O | Your right ear’s unmasked air conduction thresholds |
| X | Your left ear’s unmasked air conduction thresholds |
| Δ | Your right ear’s masked air conduction thresholds |
| [] | Your left ear’s masked air conduction thresholds |
| < | Your right ear’s unmasked bone conduction thresholds |
| > | Your left ear’s unmasked bone conduction thresholds |
| [ | Your right ear’s masked bone conduction thresholds |
| ] | Your left ear’s masked bone conduction thresholds |
Hearing Threshold
The hearing threshold represents the quietest noise audible at various frequencies. It indicates the lowest sound intensity required for you to perceive a particular sound frequency and is expressed in decibels (dB).
To determine your hearing thresholds, a hearing specialist utilizes two key tests:
1. Air Conduction
The ability to detect sounds as they travel through the air—how we normally hear—is known as your air conduction threshold.
During an air conduction test, a hearing specialist will play sounds through headphones at different frequencies and loudness levels. You’ll be asked to identify when you can hear them.
2. Bone Conduction
Bone conduction testing determines how sensitive your inner ear is and how well your auditory nerve functions.
In this part of the test, the hearing care professional uses an oscillator—a bone conduction device—to send mild vibrations (sound waves) directly to your auditory nerve.
Your bone conduction thresholds, which bypass the outer and middle ear, help identify the type of hearing loss you may have, including:
- Sensorineural Hearing Loss: caused by problems with the auditory nerve or inner ear.
- Conductive Hearing Loss: caused by issues with the middle or outer ear.
- Mixed Hearing Loss: a combination of the above two.