Hearing tests are usually carried out in an environment which is soundproofed from external noise. The person whose hearing is being tested listens to sounds transmitted by an audiologist and presses a button to signal when they have heard something. The results of the test are plotted on an audiogram.
An audiogram shows the quietest sounds you can just hear. The red circles represent the right ear and the blue crosses represent the left ear. Across the top, there is a measure of frequency (pitch) from the lower pitched sounds on the left going to higher pitched sounds on the right. Each red circle and blue cross represents the individual frequencies of sound that have been presented. These sounds are measured in Hertz. Down the side of the audiogram, there is a measure of loudness. At the top of the graph are the very quiet sounds, going down to moderate, and then very loud sounds. The points (red circles and blue crosses) marked on the graph represent the quietest sound which can be just heard. This loudness is measured in a scale called decibels (dB). Any points that are heard at 20dB or quieter are considered to be within the normal range.
The lower down the graph the points are plotted, the worse the hearing. The different shaded areas indicate the different classifications of hearing loss. For example, if an individual’s thresholds were all between 40 and 60 dB we would say they have a moderate hearing loss. The most common way of helping someone with a hearing loss is to fit hearing aids. However the worse a hearing loss is, the more difficult it is to fit hearing aids. When thresholds are above 100dB, the hearing loss may be difficult to aid as the sound quality the patient gets from the aid is likely to be poor. This is because the louder the hearing aid has to make the sound the more distortion it creates.
The audiogram gives information used to determine the most suitable help for an individual – which could be a hearing aid, cochlear implant, or other supportive device or equipment.
This audiogram shows the loudness and pitch at which environmental sounds are made.
