Interpreting the tests – Audiogram and Tympanogram

Tympanogram: Interpreting impedance results

Tympanometry is a test of middle ear functioning. It looks at the flexibility (compliance) of the eardrum to changing air pressures, indicating how effectively sound is transmitted into the middle ear. This objective test also allows us to view the functioning of the Eustachian Tube, the upper auditory pathways and the reflex contraction from the middle ear muscles. Impedance testing is crucial in distinguishing a conductive loss from a sensorineural hearing loss. A typical tympanometry result indicates the ear canal volume (cm3), the max pressure (daPa) and the peak compliance (ml).

Classifications

Tympanogram TYPE B

Type A

  • Suggests normal middle ear functioning
  • Peak is between +/- 100 daPa
  • Compliance from 0.3-1.5 ml
Tympanogram TYPE B High

Type Ad

  • Suggests a highly compliant middle ear system
  • Peak is between +/- 100 daPa
  • Compliance is more than 1.5 ml
Tympanogram TYPE C

Type As

  • Suggests a less compliant middle ear system
  • Peak is between +/- 100 daPa
  • Compliance is less than 0.3 ml
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Type B

  • Suggests middle ear involvement from fluid (middle ear effusion)
  • There is no identifiable peak
  • Ear canal volume is normal
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Type B-High

  • Suggests middle ear involvement from a perforation or patent grommet
  • There is no identifiable peak
  • Equivalent ear canal volume exceeds normal limits; much larger than 1.5cm3
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Type C

  • Suggests Eustachian Tube dysfunction (often seen just before or after effusion)
  • Peak is below – 100 daPa
  • Compliance from 0.3-1.5 ml

Audiogram – Interpreting results

An audiogram represents an individual’s hearing ability by frequency (pitch) and intensity (volume). The softest sounds that a person can hear at a particular frequency is called their hearing threshold. This is usually represented by markings on their graph; red represents the right ear and blue represents the left.

Reading an audiogram

audiogram-1

Hearing within normal limits.

audiogram-2

Bilateral moderate conductive hearing loss – this loss would warrant further medical investigation.

audiogram-4

Bilateral mild to moderately severe sensorineural hearing loss – this person would benefit from hearing aids.

audiogram-3

Bilateral moderate to profound sensorineural hearing loss – this client would most likely be a Cochlear implant candidate.

Note: It should be remembered that the audiogram quantitatively measures hearing; it doesn’t measure the client’s perceived quality of the sound.