Reading the Tympanogram

The Jerger classification, normative ranges, and a systematic reading method.

The typing of tympanometric patterns popularised by Lidén (1969) and Jerger (1970) remains in the most widespread clinical use. It is a quick visual shorthand — but it works best when backed by the actual numbers. [Lidén G 1969][Jerger J 1970][American Speech-Language-Hearing Association 1988]

The Jerger types

• Type A — peak near 0 daPa with normal amplitude: normal middle-ear pressure and mobility.
• Type As — peak at normal pressure but shallow: a stiff system, e.g. otosclerosis or tympanosclerosis.
• Type Ad — peak at normal pressure but abnormally deep: a hypermobile system, e.g. ossicular discontinuity or a flaccid drum.
• Type B — flat, no identifiable peak: e.g. effusion (normal ECV), perforation (large ECV), or occlusion (small ECV).
• Type C — peak shifted markedly negative: significant negative middle-ear pressure, e.g. Eustachian tube dysfunction. [Jerger J 1970]

Adult normative ranges

Commonly cited adult reference values are an equivalent ear-canal volume of roughly 0.6–2.0 cm³, a static admittance of roughly 0.3–1.6 mmho, a tympanometric peak pressure between about -100 and +50 daPa, and a tympanometric width up to roughly 110 daPa. Normative data are population- and age-dependent, and institutions may adopt their own; the values used here follow widely cited screening criteria. [Margolis RH 1987][Koebsell KA 1986][British Society of Audiology 2013]

A systematic reading method

• Check the ECV first — it tells you whether the system is sealed and intact.
• Find the peak pressure — is the middle ear aerated?
• Read the static admittance — is the system too stiff or too mobile?
• Read the width — a broad peak suggests early or partial loading.
• Only then assign a type, and always cross-check against audiometry, otoscopy and reflexes.

A normal-looking tympanogram does not guarantee a normal ear. Otosclerosis can produce a marked conductive loss with a near-normal trace; the absent acoustic reflex is often the more sensitive sign. Conversely, a flaccid or scarred drum can look strikingly abnormal while hearing is barely affected. [American Speech-Language-Hearing Association 1988][Jerger J 1970]

The five types at a glance

Compare the shapes side by side. Type A is the normal reference; the rest each signal a different middle-ear state.