Audiometry

• Audiometry


  Testing a patient’s hearing by playing a variety of tones and volumes using headphones (air conduction) and a bone conduction device (oscillator) that delivers sound directly to the bones of the skull
• Audiometry results are recorded on an audiogram
• Audiograms can help identify and differentiate conductive and sensorineural hearing loss
• Audiogram


  Charts that document the volume at which patients can hear different tones
• Audiogram


  The frequency in hertz (Hz) is plotted on the x-axis, from low to high pitched. In decibels (dB), the volume is plotted on the y-axis, from loud at the bottom to quiet at the top. The lower down the chart, the higher the decibels and the louder the volume. The higher up the y-axis, the more sensitive the hearing
• Hearing test


  Establishing the quietest volume at which a patient can hear each frequency. This level is plotted on the chart. The louder the sound required for the patient to hear, the worse their hearing is and the lower on the chart they will plot
• For example, a 1000 Hz sound will be played at various volumes until the patient can just about hear the sound. If this tone is heard at 15 dB, a mark is made on the chart where 1000 Hz meets 15 dB
• Hearing test process

  1. Play 1000 Hz sound at various volumes until the patient can just about hear the sound

  2. Mark on the chart where 1000 Hz meets the dB level when the sound is heard

  3. Hearing tested in both ears separately

  4. Both air and bone conduction are tested independently
• Symbols used in hearing test

  • X – Left-sided air conduction
  • ] – Left-sided bone conduction
  • O – Right-sided air conduction
  • [ – Right-sided bone conduction
• When a patient has normal hearing, all readings will be between 0 and 20 dB, at the top of the chart
• In patients with sensorineural hearing loss, both air and bone conduction readings will be more than 20 dB, plotted below the 20 dB line on the chart. This may affect only one side, one side more than the other, or both sides equally
• In patients with conductive hearing loss, bone conduction readings will be normal (between 0 and 20 dB). However, air conduction readings will be greater than 20 dB, plotted below the 20 dB line on the chart. In conductive hearing loss, sound can travel through bone but is not conducted through air due to pathology along the route into the ear
• In patients with mixed hearing loss, both air and bone conduction readings will be more than 20 dB. However, there will be a difference of more than 15 dB between the two (bone conduction > air conduction)
• Last updated

  July 2021