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 graph produced by the test, the vertical or Y axis charts the volumes of the sounds you were able to hear; these volumes are measured in decibels (dB), ranging from the faintest volumes (0dB) to the loudest measured in this test (100dB). 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. 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. During the test, sounds are played at their lowest possible decibel levels, and then the volume is slowly raised, and you indicate to the audiologist when you can first hear them.
This process is repeated at additional frequencies. This produces the audiogram, a series of dots across the graph that represent the volume at which you first were able to hear sounds at different frequencies. In theory, this line of dots should be fairly straight, showing that you heard all frequencies at about the same volumes, but even in people with perfect hearing there are always small variations. 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. An inability to hear low-volume high-frequency sounds could indicate a type of hearing loss caused by exposure to loud sounds, called noise-induced hearing loss (NIHL). A significant inability to hear low volumes at all frequencies might indicate otosclerosis, a common form of 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.