The test can be done in three ways:
- Sitting in a sound-proof room. The tone audiogram is made with the help of a headphone. This measures the air conduction.
- Another way to do the measurement is to, apart from the headphone, place a vibrating block behind the ear as well. The bone directly behind the ear can transfer sound vibrations to the cochlea and the auditory nerve. This is called bone conduction. The bone conduction test can determine to what extent you can hear tones of different levels of loudness and pitch in the cochlea.
- Finally, the measurement can be done by means of a headphone through which you hear noise on one side. For example, when noise is given on the right ear, this right ear cannot receive sound given to the left ear. This is called ‘masked measurement’.
The result of a tone audiogram hearing test is recorded in a diagram.
An audiogram has to axes. The vertical axis indicates the volume and intensity of the tone. This is measured in decibel (dB). The lower on the axis, the louder the tone. The weakest tone (0 dB) is at the top of the axis. Usually, a human being can just hear this tone.
The horizontal axis indicates the frequency and pitch of the tone. This is measured in Hertz (Hz). The further to the right on the axis, the higher the frequency. This is just like a piano: the further the key is placed on the right side, the higher the tone. The frequency of a normal conversation is between 500 Hz and 3000 Hz.
An audiogram shows the results for the right ear with a red line and for the left ear with a blue line. The lines indicate the hearing threshold for each ear. The results for both ears may differ.
An audiogram rarely shows a straight line. With perceptive deafness we often see the line sharply drop at the high tones. The general rule is: the higher the lines in the audiogram, the better. The lower, the worse.