Reading the Graph
An audiogram is a graphical representation of pure tone audiometry test results. It charts the softest sounds (threshold) that a patient can hear at each frequency tested. The frequency of the tone is displayed across the x-axis (horizontal), while the loudness of sound is displayed along the y-axis (vertical). Frequency is measured in Hertz (Hz) and intensity is measured in Decibels (dB).
There are different symbols used to differentiate between the thresholds based on the transducer used. Below is a chart of the commonly used symbols on an audiogram. Air conduction testing is performed using earphones, inserts, or speakers. Sound is sent through the middle ear to the inner ear. For bone conduction testing, a bone vibrator is placed behind the ear to deliver sounds directly to the inner ear, bypassing the middle ear.
Degree of hearing loss
Once thresholds have been plotted on an audiogram, the degree of hearing can be determined. For adults, normal hearing is considered to be thresholds 25 dB or less.
|
Intensity (in dB) |
Degree of hearing loss |
|
0-25 dB |
Hearing is within normal limits |
|
25-35 dB |
Mild hearing loss |
|
40-65 dB |
Moderate hearing loss |
|
70-90 dB |
Severe hearing loss |
|
95+ |
Profound hearing loss |
Types of hearing loss
The type of hearing loss is determined based on the difference between the air conduction and bone conduction thresholds.
Sensorineural hearing loss reveals a problem with the inner ear organ or auditory nerve pathway. If air conduction and bone conduction thresholds are within 15 dB of one another, the hearing loss is considered sensorineural.
Conductive hearing loss reveals a problem in the middle ear system. If air conduction thresholds show a hearing loss, but bone conduction thresholds are within normal limits, the hearing loss is considered conductive.
Mixed hearing loss reveals a problem with both the middle ear system and the inner ear organ. A hearing loss evident through bone conduction testing and a greater degree of hearing loss through air conduction testing with a difference of 15 dB or more between thresholds would be considered mixed.
If you would like to have your hearing tested, or if you have any questions about your specific audiogram, please make an appointment with your JHBI healthcare provider.