Audiogram Interpretation for GP Registrars

An audiogram records the results of pure tone hearing tests. There are several common patterns on the audiogram.
An audiogram plots the softest sound that can be heard across a range of low to high pitch sounds. It graphs frequency (from low to high pitch sounds) against hearing threshold (volume of sound, from soft to loud volume).
There are commonly accepted ranges for normal, mild, moderate, severe and profound hearing loss. In adults, normal hearing is often 0-25 dB. Note that the baseline (0 dB) represents normal hearing, not the absence of sound completely.
The results are plotted with different symbols for air conduction in the right (O) and left (X) ears, +/- bone conduction in the right ([) and left (]) ears. Here is an example of a normal audiogram:

Common Patterns

  • Audiograms show different patterns for conductive, sensorineural or mixed hearing loss.

  • Normal hearing.

    Conductive hearing loss. There is a mild loss of air conduction in both ears, but bone conduction is still normal.

    Sensorineural hearing loss. Air and bone conduction are both equally abnormal.

    Mixed hearing loss. There is a gap between air and bone conduction, but neither is normal.

  • Common clinical patterns include things like ear infections, impacted wax, presbycusis and noise-induced hearing loss.
  • Otitis media. There is a bilateral conductive hearing loss – air conduction is reduced but bone conduction is still normal.

    Presbycusis, or age related hearing loss. There is downsloping symmetrical hearing loss, worse at higher frequencies.

    Noise-induced hearing loss (industrial deafness). There is a notch around 4000 Hz. The patient may not understand speech well, as they are likely to miss the high frequency consonants of speech.

    Perforation. There is a mild unilateral conductive loss. Earwax might give a similar conductive loss, but may also be likely to be bilateral.

    Meniere disease. There is asymmetric unilateral hearing loss, upward sloping (worst in low frequencies).

    Ototoxicity, such as gentamicin or cisplatin / carboplatin. There is a symmetrical downsloping sensorineural loss.

    Otosclerosis. Early otosclerosis gives a bilateral mild-moderate conductive loss, greater in lower frequencies. There is a 2000 Hz Carhart notch in bone conduction. Late otosclerosis may give a mixed pattern.

    Exercise: Can you identify these patterns?

    Normal audiogram.
    Bilateral mild conductive hearing loss, i.e. bilateral Otitis Media with Effusions.
    Bilateral mixed hearing loss.
    Right unilateral sensorineural hearing loss.
    Presbycusis
    Noise-induced hearing loss. Note the notch at 4000Hz. This is common but not diagnostic – there are other causes of this notch apart from noise.
    Meniere disease in the right ear (unilateral sensorineural loss).
    Unilateral mild conductive hearing loss in the right ear, ie impacted wax or perforated tympanic membrane.
    Otosclerosis. Note the Carhart notch at 2000Hz.

    Exercise: Which of the following are true?

    • The X-axis represents pitch.
      Yes, the x axis of the audiogram is the pitch (frequency) of the sound tested, with deep sounds on the left and high sounds on the right (like looking at a piano keyboard).
    • Hearing threshold is measured in decibels (dB).
      Yes, the softest volume that a person can hear (at least 50% of the time) is recorded on the audiogram and it is measured in decibels.
    • O = left ear air conduction
      No, O = right ear air conduction.
    • X = right ear bone conduction
      No, X = left ear air conduction.
    • [ = right ear bone conduction
      Yes, [ = right ear bone conduction.
    • ] = left ear air conduction
      No, ] = left ear bone conduction.
    • 0 dB on the y axis is absolute silence.
      No, 0 dB is the baseline threshold for normal hearing. Some patients can have hearing that is above this level, ie they can hear sounds that are even quieter than normal (such as -10 dB).
    • Middle ear effusions cause a conductive loss.
      Yes, middle ear effusions will affect air conduction but bone conduction may still be normal.
    • Presbycusis affects high sounds more than low.
      Yes, presbycusis (age-related hearing loss) affects the higher frequencies most.