Interpreting Your Tympanogram Results

The graphical representation of a person’s function of the middle ear measured using tympanometry is known as a tympanogram. The graphical representation shows the patient’s ear canal volume (an indicator for perforated tympanic membrane or impacted cerumen), compliance of the tympanic membrane/ middle ear (an indicator for fluid in the middle ear, ossicular discontinuity, otosclerosis etc), and the middle ear pressure also known as the tympanometric peak pressure (an indicator for eustachian tube dysfunction etc).

The tympanogram depicts both tympanogram tracings and numeric data obtained from the tympanometry measurement system. The tympanogram tracings and numeric data obtained from the test are usually interpreted based on the Liden (1969)1 and Jerger (1970)2 classifications and Margolis and Heller (1987)3 normative data/ or the British Society of Audiology4 normative data. It is important to note that recently, there has been more varying normative data for specific populations, and interpretations of your tympanogram can be based on the normative data which your institution uses.

 

Numeric data shown on a Tympanogram

In general, there are four objective data collection points with specific terms yielded by the tympanometer. Below are the four objective data terms, definition, and the numeric data yielded. 

  1. Equivalent Ear Canal Volume (ECV): This is the estimated volume of the ear canal volume from the front of the probe tip. The range of normal ECV is age-dependent and is measured in cm3.
  2. Compliance/ Static Admittance (SA): This is the maximum amount of acoustic energy absorbed by the middle ear system. This indicates the morbidity of the middle ear system (and the tympanic membrane) measured in mmho or cm3.
  3. Tympanometric Peak Pressure (TPP)/ Middle Ear Pressure: This is the pressure in which there is greatest absorption of acoustic energy in the middle ear system. This value estimates the middle ear pressure and is measured in daPa. 
  4. Tympanometric Width (TW): This is the pressure interval where a horizontal line intersects the tympanogram tracing at 50% of its peak height, measured in daPa. 

The above mentioned objective data (four) are interpreted using normative data. Normative data can be used to help determine when an individual’s ECV, SA, TPP, and/ or TW is within normal ranges — and what the implications are.

 

Interpretation of a Tympanogram

This section will cover basic tympanogram interpretations based on Liden (1969)1 and Jerger (1970)2 classifications and British Society of Audiology4 normative data for Tympanometry. The normative data on the table below shows normative data for patients older than 1 year of age, when the clinician is using a 200 daPa/s pump speed and a 226 Hz probe tone. Most audiology clinics tympanometers use the 200 daPa/s pump speed and a 226 Hz probe tone – as a result, this section will only cover normative data for these settings.

Intepreting your tympanogram results table 1

Tympanograms are classified as Type A, B, C, AS, and AD. Each classification falls in or out of the normative range. The below classifications are specific to patients tested using a 226 Hz probe tone — as examples. 

Note: Tympanogram classifications differ between audiologists, guidelines, countries, and clinics. This is only a guide and should be used in conjunction with other audiological test results and own clinical knowledge and research.

 

Type A

Type A tympanogram indicates normal middle ear status. This is a tympanogram curve that has a maximum height that occurs at a pressure that approximates 0 daPa. A Type A tympanogram has an ECV (or Vea) that falls within 0.6-2.0 cm3, Compliance/ SA (or Ya) that falls within 0.3-1.6 cm3, and a TPP that is around -100-(+50) daPa as indicated in the norm table above. ECV that is more than 2.5 cm3 may be indicative of a perforated tympanic membrane.

ECV: 0.6 — 2.0 cm3
Static Admittance: 0.3 — 1.6 cm3
Middle Ear Pressure: -100 — (+50) daPa

Interpreting your tympanogram results type A

Type AS

Type AS tympanogram indicates a middle ear system that has a decreased mobility. This is shown by having a normal tympanogram but with a low compliance/ SA reading. For example, a static admittance/ compliance of less than 0.3 cm3 is indicative of this type of tympanogram. This tympanogram is indicative of ossicular fixation, or some fluid in the middle ear causing restricted middle ear mobility.

ECV: 0.6 — 2.0 cm3
Static Admittance: <0.3 cm3
Middle Ear Pressure: -100 — (+50) daPa

Interpreting your tympanogram results type As

Type AD

Type AD tympanogram has a curve that demonstrates a high compliance/ static admittance (Ya). A high static admittance (> 1.6 cm3 ) is as a result of an overly mobile tympanic membrane/ middle ear system. This type of tympanogram is indicative of ossicular discontinuity or a hyperflaccid tympanic membrane (often as a result of a tympanic membrane that has healed from a perforation and is now thinner and thus overly compliant).

ECV: 0.6 — 2.0 cm3
Static Admittance: > 1.6 cm3
Middle Ear Pressure: -100 — (+50) daPa

Interpreting your tympanogram results type Ad

Type B

Type B tympanogram has a flattened curve with a low admittance. Many clinics and studies consider this type of tympanogram as an abnormal tympanogram. A Type B tympanogram can have either a normal ECV, low ear canal volume (<0.3 cm3) which could indicate partial ear canal occlusion with cerumen, or a high ear canal volume (>2.5 cm3) which is indicative of a tympanic membrane perforation. A type B tympanogram is often indicative of tympanic membrane with decreased mobility as a result of middle ear fluid (or otitis media with effusion).

ECV: 0.6 — 2.0 cm3
*ECV: > 2.5 cm3 (Type B tympanogram, high ear canal volume – Possible perforation of the tympanic membrane)
Static Admittance: very low

Interpreting your tympanogram results type B

Type C

Type C tympanogram demonstrates a significantly negative pressure in the middle ear (>-150 daPa). A negative middle ear pressure is indicative of a retracted tympanic membrane. In most cases, this type of tympanogram tracing shows a transition from normal middle ear to middle ear filled with fluid.

ECV: 0.6 — 2.0 cm3
Static Admittance: 0.3 — 1.6 cm3
Middle Ear Pressure: > -150 daPa

Interpreting your tympanogram results type C

Reference

  1. Liden, G. (1969). The scope and application of current audiometric tests. Journal of Laryngology and Otology, 83, 507-520.
  2. Jerger, J.F. (1970). Clinical experience with impedance audiometry. Archives of Otolaryngology, 92, 311-324.
  3. Margolis, R. H., & Heller, J. W. (1987). Screening tympanometry: criteria for medical referral: original papers. Audiology, 26(4), 197-208.
  4. British Society of Audiology. (2013). Tympanometry: Recommended Procedure.