Hearing test results are illustrated with a standardized graph called an audiogram. Separate results for the left and right ears are indicated by the placement of an O or X on a vertical and horizontal axis to show the severity and configuration of hearing loss, with placement in the bottom half of the graph indicating severe or profound loss. Normal range for an adult typically falls between -10 decibels (dB) and 25 dB. Different ranges are expected for children because they do not respond to test prompts as accurately as adults.
An individual's hearing test results can be interpreted by noting the placement of the O and X on the audiogram. The O, or sometimes a triangle shape, indicates the right ear; the left ear is indicated with the X, or sometimes with a square. The audiogram can help to diagnose hearing loss as conductive, sensorineural, or mixed. It can also show whether the loss is unilateral, affecting only one ear, or bilateral, affecting both ears. Typically, the results for the left and right ears are not identical.
In an audiogram showing hearing test results, the placement of O and X indicators is based on the assessment of the individual's ability to perceive specific frequency ranges and degrees of loudness. The audiogram uses horizontal lines to show loudness, with the softest sounds at the top of the graph and the loudest sounds at the bottom. Vertical lines represent specific frequencies or pitches, measured in Hertz (Hz). The lowest pitch, such as a bass drum, is on the far left and the highest pitch, such as the chirping of a bird, is on the far right.
In an adult, hearing test results are considered to be normal when the ear perceives sound in the decibel range of -10 dB to 25 dB. Mild hearing loss is indicated by a range of 26-40 dB, while moderate loss is a range of 41-55 dB. A range of 56-70 dB is considered moderately severe; 71-90 dB is severe; and over 90 dB is considered profound hearing loss.
Two types of hearing loss that can be evaluated by hearing test results are conductive and sensorineural. In conductive hearing loss, which can sometimes be surgically or medically corrected, sound does not travel efficiently through the ear canal. In sensorineural hearing loss, there is damage to the inner ear or to the nerve pathways to the brain from the inner ear; this is the most common kind of permanent hearing loss and cannot typically be corrected with surgery.