An audiogram is the output – in the form of a graph – of a test performed to assess the state of your hearing, and to help determine whether you have suffered any hearing loss. The audiometry test is very quick and comfortable. The test measures your ability to hear sounds at various decibel levels and frequencies. On the resulting audiogram, the Y axis (vertical axis) is volume in decibels (db). The testing range is generally 0 to 100 decibels where 0 is very faint and 100 is quite loud. On the other horizontal or X axis, you see the frequencies of different sounds, measured in Hertz (Hz); the frequencies range from 100Hz (the lowest bass frequency sounds measured in this test) to 8000Hz (the highest treble frequency sounds measured).
The instrument used to create the audiogram is a device called an audiometer. To ensure accuracy in the hearing test, you will generally be given a set of foam-padded headphones to wear. Tones at different volumes and frequencies are sent through the special headphones. Sounds heard through bone conduction are measured by a headband that you may be asked to wear around your forehead. The test generally starts with the lowest volumes possible. The specialist administering the test will gradually raise the volume until you are first able to hear it.
Then the process repeats with a sound at a different frequency. For each frequency tested, the volume at which you are first able to hear it is plotted on a chart – this is the audiogram. Equal hearing across all frequencies appears as a straight horizontal line of dots on the audiogram. But, the lines for real people are rarely straight even if they have perfect hearing. Small variations are normal and expected. When the audiologist sees larger variations, however – not being able to hear sounds in the low frequencies except at high volume, for example – this could demonstrate a type of hearing loss caused by M√©ni√®re’s disease. Alternatively, if you can only hear high-frequency sounds at a high volume, that might be an indicator of a condition called NIHL, or noise-induced hearing loss. If your audiogram shows an inability to hear low volumes across nearly all frequencies, you may have sensorineural hearing loss.
The audiogram, whatever it shows, is one of the primary tools use to diagnose the state of your hearing, and to make recommendations as how best to improve it.