To measure the extent of your hearing loss you may be asked to take a comprehensive hearing test. An audiogram is the result of that test in the form of a graph. The test is painless, and can be completed in only a few minutes. On the audiogram graph, the Y or vertical axis represents the intensity of sounds that you were able to hear, measured in decibels (dB), from 0 (the faintest) to 100 (the loudest). The X or horizontal axis represents the frequency of the sound in Hertz (Hz), on a scale from 100Hz (the lowest frequency sounds tested, equivalent to low bass notes in the second octave of a piano) to 8000Hz (the highest frequency sounds tested, equivalent to the highest notes of bird songs).
A device called an audiometer is use to take the measurements plotted on the audiogram. During the test, the audiologist asks you to wear a pair of padded headphones, and then plays sounds at different frequencies through them, at different volumes. (Note that some of the sounds your brain registers during the hearing test actually arrive there via bone conduction, so you may be asked to where a headband around your forehead that measures this activity.) 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.
The specialist will then repeat the process starting with a tone at a new 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. Ideally, the line represented by the different dots would be straight, indicating equal hearing ability at all frequencies, but in practice everyone’s audiogram will be slightly different, even if they have perfect hearing. 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. A significant inability to hear low volumes at all frequencies might indicate otosclerosis, a common form of sensorineural hearing loss.
These are just three example of data that your hearing specialist may glean from your audiogram. It is a vital tool in assessing the type of hearing loss you have and the treatments that are most suitable for you.