Diagnostics: Tympanometry

Tympanometry is a quick, painless test that shows how freely the eardrum moves and whether the middle ear is healthy.

What Tympanometry Is

Tympanometry is a quick, painless test that checks how well the eardrum and middle ear are working. The middle ear is the small air-filled space just behind the eardrum. Tympanometry does not measure hearing directly. Instead, it measures how freely the eardrum moves and whether the middle ear is healthy, which helps explain many causes of hearing trouble, ear pressure, or ear infections. Hearing itself is measured by audiometry, and the two tests are often performed together.

How the Test Is Done

A soft rubber tip attached to a small handheld or desktop device is placed snugly in the opening of the ear canal to form a seal. The device then gently changes the air pressure in the ear canal, plays a low tone, and measures how much sound bounces back off the eardrum. The test takes only a few seconds per ear. It requires no active response, such as button-pressing or raising a hand, so it can be used for young children and others who cannot respond to a standard hearing test. It may feel like a brief change in ear pressure or a faint tone, and it can feel odd or startling to some children, but it does not hurt. The ear is usually looked at with an otoscope first to check for earwax or other blockage that could affect the results.

What a Tympanogram Shows

The result is a graph called a tympanogram. It plots how easily the eardrum moves (up and down on the graph) against the air pressure applied in the ear canal (side to side). A healthy eardrum moves best when the pressure in the ear canal matches the pressure in the middle ear, creating a peak on the graph. The shape and position of that peak tell the story of what is happening behind the eardrum.

Three measurements matter most:

• Middle ear pressure: Where the peak sits on the graph. Normal pressure is near zero. A peak shifted toward negative pressure suggests the middle ear space is under a vacuum.

• Compliance (mobility): How tall the peak is, meaning how freely the eardrum moves. A very small peak means a stiff eardrum; a very tall peak means an unusually floppy one.

• Ear canal volume: An estimate of the amount of air space in front of the probe. This helps tell whether the eardrum is intact.

Ear Canal Volume Explained

Ear canal volume is especially useful when the graph is flat. A normal volume with a flat graph usually points to fluid behind the eardrum. A low volume usually means the probe tip is up against the ear canal wall or blocked by earwax, and the test simply needs to be repeated after clearing the ear. A high volume with a flat graph suggests the eardrum is open to the middle ear, because of a hole (perforation) or a working ear tube.

Type A (Normal)

A Type A tympanogram has a clear peak near normal (zero) pressure. It indicates a healthy, air-filled middle ear with an eardrum that moves normally, and a low chance of fluid.

Type As (Shallow Peak)

Type As ("s" for shallow or stiff) has a peak in the normal pressure range but a smaller-than-normal peak. It means the eardrum moves less than expected, or is stiff. This pattern can be seen with conditions that stiffen the eardrum or the tiny middle ear bones, such as otosclerosis or scarring.

Type Ad (Very Tall Peak)

Type Ad ("d" for deep) has a peak in the normal pressure range but an unusually tall peak. It means the eardrum is more floppy or mobile than normal. This can be seen with a very loose eardrum or a break in the chain of middle ear bones.

Type B (Flat)

Type B is a flat line with no clear peak. When combined with a normal ear canal volume, it usually means fluid is filling the middle ear. Along with the ear canal volume, a flat line can also indicate a blocked probe, an eardrum perforation, or an ear tube.

Type C (Negative Pressure)

Type C has a clear peak but shifted toward negative pressure. It indicates a vacuum in the middle ear, most often from Eustachian tube dysfunction, when the tube that ventilates the middle ear is not opening well. This is common with colds, allergies, or air-pressure changes and can precede a build-up of fluid.

Common Conditions and What They Look Like

• Fluid in the middle ear (otitis media with effusion): Typically a flat Type B graph with a normal ear canal volume. Fluid keeps the eardrum from moving. More information is available on the middle ear fluid page.

• Eustachian tube dysfunction: Often a Type C graph, showing negative pressure from poor ventilation of the middle ear.

• Eardrum perforation or an ear tube: Usually a flat graph with a high ear canal volume, because the air space now includes the middle ear.

• Otosclerosis: May show a Type As (shallow) pattern, reflecting stiffening of the middle ear bones.

How Tympanometry Relates to Hearing Tests

Tympanometry works alongside audiometry (the standard hearing test) rather than replacing it. Audiometry measures how soft a sound a person can hear at different pitches. Tympanometry explains the mechanical reason behind certain hearing results. When hearing loss is caused by a problem carrying sound through the ear canal, eardrum, or middle ear (called conductive hearing loss), the tympanogram is often abnormal, showing fluid, negative pressure, or a stiff or floppy eardrum. When hearing loss comes from the inner ear or hearing nerve (sensorineural hearing loss), the tympanogram is usually normal because the eardrum and middle ear are working fine. Reading the two tests together helps pinpoint where a hearing problem is coming from. More background is available on the hearing loss conditions page.

The Bigger Picture

Tympanometry is a fast, safe, and objective way to check the middle ear. It cannot see inside the ear on its own, so it is combined with an ear exam and hearing testing. The pattern of the tympanogram, together with the ear canal volume, helps distinguish among fluid, pressure problems, a perforation or tube, and stiffening of the ear, each of which points to a different consideration in care.

Example Tympanograms

The illustrations below show simplified examples of the main tympanogram types. They are examples only and do not represent any individual's results.