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What is tympanometry?

Fact Sheet


Tympanometry is a technique used to look at the function of the middle ear. It is NOT a hearing test. It is a test used together with otoscopy (looking into the ears) and audiometry (testing the hearing) and is useful in helping to determine how the middle ear is functioning.

How does a tympanometer work?

The procedure of tympanometry involves inserting a probe into the outer ear canal and creating an air-tight seal. The probe contains a tiny speaker, a microphone and an air pump. The air pump changes the air pressure range (typically +200 daPa to –400 daPa) in the ear canal. The speaker introduces a calibrated tone into the ear canal, which changes in frequency and loudness. Some of the sound produced by the speaker will be passed through the middle ear, while some of the sound will be reflected back off of the tympanic membrane. The microphone measures the amount of reflected sound in the ear canal. The “compliance” of the eardrum and middle ear (i.e. how well this system responds to sound) is then determined by the tympanometer as the air pressure changes.

What is a tympanogram?

A tympanogram is a chart which can tell us how well the middle ear is functioning.

What does a tympanogram tell us?

Tympanograms are classified into types according to the shape of the tympanometric trace (“peak”), which is dependent upon the middle ear pressure, and the middle ear compliance.

A tympanogram can provide three helpful pieces of information:

Middle ear pressure
This is the air pressure of the air contained within the middle ear. It is shown by where the “peak” of the tympanometric trace falls along the pressure axis.
Middle ear pressure values ranging from +50 daPa to –200 daPa for children, and +50 daPa to –50 daPa for adults is generally considered normal.

- The compliance of the middle ear system is a measure of how well the system responds to sound. This is shown by the height of the “peak”.
- Middle ear compliance values from 0.3 to 1.5 cc are usually considered normal.

 Equivalent volume of the ear canal
- Normative ear canal volumes vary as a function of age. Typically for children a volume range of 0.5 to 1.5 cc is typically considered normal, while for adults the range is 0.5 to 2.00 cc. This value is reported by the tympanometer, but not shown on the tympanogram graph.

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