What is an audiogram?

During your clinician hearing test, an audiogram is created using an audiometer. For this, your clinician will play a specific sound to you through headphones. The individual sounds start at a very quiet level and gradually become louder. The reading is taken for each ear individually. The quietest sound that you can hear is identified by this frequency and intensity. This combination of frequency and intensity is called the hearing threshold level. The audiogram is a reflection of your hearing ability. It shows how far your hearing ability deviates from normal hearing ability, and, if there is a discrepancy, what the cause of the hearing loss might be.

Deviations may take various forms and have various degrees of severity. Depending on the part of the ear that is affected, four main types of hearing loss can be distinguished:

• Conductive hearing loss,
• Sensorineural hearing loss,
• Combined hearing loss,
• And neural hearing loss.

The tone audiometry is followed by a speech audiometry (speech intelligibility test). This determines the extent to which hearing loss affects the understanding of speech.

An audiogram features two axes. Loudness and intensity can be read on the vertical axis. These are measured in decibels (dB). The lower the point on the axis, the louder the tone. The quietest tone (0 dB) is at the top of the axis. A person can normally still hear this tone.
 
Tone frequency and pitch are read along the horizontal axis. This is measured in Hertz (Hz). The further right along the axis, the higher the frequency. This direction is similar to a piano: The further right the key, the higher the tone. The frequency of a normal conversation is between 500 Hz and 3,000 Hz.

During a hearing test, the results are recorded on the audiogram using a red mark for the right ear and a blue mark for the left ear. Connecting these marks results in lines that show the hearing threshold level for each ear. It is quite possible to obtain different results for each ear.
 
As a general rule, the further the hearing curve is from the line of the normal hearing range, the greater the hearing loss.

Sound level is measured in decibels (dB) using the decibel scale. The decibel scale is a logarithmic scale in which the doubling of the sound pressure level corresponds to a level increase of 6 dB. Decibels are not fixed values like volts or meters. The value of a dB depends on the respective context. It is not only used to measure the sound level, but also in antenna technology or radar metrology.

Here are some examples of different volumes, measured in decibels:

• 180 dB: a rocket launch
• 140 dB: a jet plane
• 120 dB: a rock band
• 110 dB: loud thunder
• 90 dB: city traffic
• 80 dB: a loud radio
• 60 dB: a conversation at normal volume
• 30 dB: whispering
• 0 dB: the quietest sound that can be heard by the human ear

Tone frequency is the number of vibrations in a sound wave per second. The unit of measurement is the Hertz (Hz). The higher the number, the higher the frequency. Vibrations between 20 and 20,000 Hertz are interpreted as sounds by the average person. The twittering of birds is one example of a high tone. Low tones include distant thunder or a tone on a bass guitar.
 

High-frequency hearing loss means that the affected person has problems starting with impairment in the higher frequencies only. These include sibilants (-s-, -f-, or –sh-) and consonants. Those affected find it difficult to hear tones with high frequencies, such as doorbells and telephones, or children’s voices. Lower frequencies also become harder to perceive as the impairment progresses.