Tympanic membrane perforation
Type BReflex: absentDecay: n/aAir–bone gap: Conductive, variable
A flat trace with an abnormally LARGE equivalent ear-canal volume, because the probe now measures canal plus middle-ear space.
Audiogram & tympanogram
Audiogram
Tympanogram
Reading the two together
Loss type: conductiveMean air-bone gap: 25 dBAir PTA: 32 dB HLDegree: mild
An air-bone gap with normal bone thresholds — the lesion is in the outer or middle ear.
A conductive loss weighted toward the low frequencies — the air-bone gap is largest at 250–500 Hz and tapers off higher up. Larger perforations add more high-frequency loss. Bone thresholds stay normal.
The audiogram tells you how much hearing is lost and where the lesion sits (conductive vs sensorineural); the tympanogram tells you what the middle ear is doing mechanically. Read as a pair, they pin down the diagnosis far more tightly than either does alone.
Teaching point
An unexpectedly large ECV with a flat trace is the giveaway for perforation — the seal cannot pressurise an open system.
References
- Fowler CG, Shanks JE (2002). Tympanometry. Handbook of Clinical Audiology (5th ed.), J. Katz (Ed.), pp. 175–204. Lippincott Williams & Wilkins.
- Katz J (Ed.) (2015). Handbook of Clinical Audiology (7th ed.). Wolters Kluwer.