A tympanogram is a graph that shows how well your eardrum moves in response to changes in air pressure. It’s produced by a quick, painless test called tympanometry, which helps determine whether fluid, pressure problems, or other issues are affecting your middle ear. The entire test typically takes less than a minute per ear and is one of the most common ways to evaluate ear problems in both children and adults.
How the Test Works
During tympanometry, an audiologist or technician places a small probe (similar to an earbud) into your ear canal. The probe has three tiny openings, each with a different job: one sends a low-pitched tone into your ear, one changes the air pressure inside the ear canal, and one records how your eardrum responds to those pressure changes.
As the air pressure sweeps from positive to negative (typically +200 to −400 decapascals), your eardrum stiffens and relaxes. At the extreme pressure points, the eardrum becomes so stiff that almost no sound passes through, which lets the device measure just the ear canal itself. At the pressure where your eardrum moves most freely, the instrument records peak sound transmission. The result of all this is your tympanogram: a curve plotted on a graph with air pressure on the horizontal axis and eardrum movement (called admittance) on the vertical axis.
You’ll feel a brief sensation of pressure in your ear, similar to what you might feel during altitude changes. You don’t need to do anything during the test. Just sit still, avoid swallowing or talking, and it’s over in seconds.
Reading the Results: Types A, B, and C
Tympanograms are classified using a system developed by audiologist James Jerger. The three main patterns are Type A (normal), Type B (flat), and Type C (shifted).
Type A: Normal
A Type A tympanogram shows a smooth, peaked curve with the highest point near zero pressure. This means your eardrum moves freely and your middle ear pressure is balanced. The peak is neither too tall nor too short, and the curve has a normal width. Two subtypes exist: Type As shows a shorter, stiffer peak (which can indicate a stiffened middle ear chain, sometimes from a condition like otosclerosis), while Type Ad shows an unusually tall, floppy peak (which can suggest a loose connection in the tiny bones behind the eardrum or an extremely flexible eardrum).
Type B: Flat
A Type B tympanogram is essentially a flat line with little or no peak. This is clearly abnormal and means the eardrum is barely moving. The most common cause is fluid trapped behind the eardrum, as seen in middle ear infections or persistent fluid buildup (otitis media with effusion). However, a flat result can also show up if earwax is blocking the probe, if a tube is in place, or if there’s a perforation in the eardrum.
To tell these apart, your provider looks at the ear canal volume measurement. A normal ear canal volume with a flat trace points toward fluid behind an intact eardrum. An unusually large volume suggests a perforation or open tube, because the probe is effectively measuring the middle ear space as well. Normal ear canal volume ranges from 0.3 to 1.0 mL in children and 0.65 to 1.75 mL in adults.
Type C: Negative Pressure
A Type C tympanogram still has a peak, but it’s shifted to the left of the graph, into the negative pressure range. This indicates that the pressure inside your middle ear is lower than the air pressure outside. The usual culprit is Eustachian tube dysfunction, where the narrow tube connecting your middle ear to the back of your throat isn’t opening properly to equalize pressure. Allergies, colds, and sinus congestion are common triggers. In normal ears, the peak pressure falls roughly between −83 and +50 decapascals. A peak well below that range signals a problem worth monitoring.
How Accurate Is It?
Tympanometry is particularly good at detecting middle ear fluid. Studies comparing tympanogram results to what surgeons actually find during ear tube placement consistently show high sensitivity. One study reported 86% sensitivity and 72% specificity, meaning it correctly identified fluid about 86% of the time and correctly ruled it out about 72% of the time. Other studies have found sensitivity as high as 96 to 97%, though specificity varies more widely (57 to 98% depending on the study population and methods).
In practical terms, a flat Type B result strongly suggests fluid is present. A normal Type A result is reassuring. Where tympanometry is most valuable is in ruling out fluid: studies show its negative predictive value can reach 97%, meaning that when it says there’s no fluid, it’s almost always right.
Why the Test Differs for Babies
Standard tympanometry uses a 226 Hz probe tone, which works well for older children and adults. But infant ear canals and eardrums have different physical properties due to their still-developing anatomy. In babies under about 6 months old, the standard tone can produce misleading results, sometimes showing a normal-looking curve even when fluid is present.
For this reason, audiologists use a higher-frequency 1,000 Hz probe tone for infants younger than 6 to 7 months. This higher tone is more sensitive to the actual middle ear conditions in this age group. After about 9 months, the standard 226 Hz tone becomes reliable.
What a Tympanogram Does Not Tell You
A tympanogram measures how the eardrum and middle ear system move. It does not measure hearing itself. You can have a perfectly normal tympanogram and still have hearing loss caused by inner ear or nerve problems. Similarly, an abnormal tympanogram doesn’t automatically mean you have significant hearing loss, though middle ear problems often do reduce hearing temporarily.
That’s why tympanometry is usually done alongside a standard hearing test (audiogram) rather than as a standalone assessment. Together, the two tests give a much clearer picture. The tympanogram identifies the mechanical problem, and the audiogram reveals whether and how much it’s affecting your hearing.