Hearing tests are conducted by qualified professionals called audiologists. They have special training that allows them to measure both the level of deafness and the impact that it has on the individual’s ability to perceive sound, especially speech.
Hearing tests are done in a soundproof environment. The individual wears headphones and what are called pure tone sounds are used at varying pitches (frequencies) and at varying decibels (loudness) and the individual is asked to respond each time s/he hears a sound, regardless of how faint it is. Each ear is tested separately.
The softest sounds that are reported as heard are recorded and this is called the threshold of hearing. The audiologist records this information onto an audiogram.
What we hear – or don’t hear – is then broken into categories, which are:
Normal hearing: 0-25 decibels
Mild hearing loss: 26-40 decibels
Moderate hearing loss: 41-55 decibels
Moderately severe: 56-70 decibels
Severe deafness: 71-90 decibels
Profound deafness: greater than 90 decibels