A Guide to Tympanometry: Purpose, How it Works and Types of Tympanogram Readings

Jul 28, 2022

Article by Hearing Partners, contributed by Jennifer Lee, Senior Clinical Audiologist at Hearing Partners

Tympanometry is an assessment that measures the middle ear function. It evaluates how the eardrum responds to changes in air pressure within the ear canal. A tympanogram is a graphical representation of the results of this examination. The test and the interpretation of the results will be carried out by a trained audiologist.

In this article, we’ll share the purpose of tympanometry, how it works and the various types of tympanogram readings. We’ll also cover some of the frequently asked questions about this assessment.

Purpose of Tympanometry

A tympanometry test can be helpful in highlighting problems with the middle ear and disorders that may potentially result in hearing loss. Some common issues identified through this test include:

  • Otitis media with effusion (OME), otherwise known as a middle ear infection
  • Abnormal ear pressure
  • Perforated ear drum 
  • Eustachian tube dysfunction, causing an inability to equalise middle ear pressures

How Does Tympanometry Work?

Audiologist using an otoscope to look inside patient's ear

Before the test

Before starting the test, the audiologist or hearing care professional may use an otoscope to look inside your ear canal. This is done to ensure that your ear canal is clear of earwax or any foreign objects.

During the test

A probe, which is attached to a tympanometer, will be placed into your ear canal and positive and negative air pressure will be applied to the middle ear. This is accompanied by a constant low-pitched tone. For infants, a high-pitched tone will be used.

The test records the amount of sound that is absorbed or reflected by the middle ear as the pressure changes. The results will be represented graphically in a tympanogram.

Types of Tympanogram Readings

The x-axis of a tympanogram measures the air pressure in the ear (daPa) while the y-axis represents the compliance (ml), which is the ability of sound to pass through the eardrum to the middle ear. The graph also provides information about the ear canal volume (cm3).

Note: Different hearing care clinics and audiologists may classify the readings differently. This section serves to provide general information and you’re advised to consult your audiologist regarding your test results for an accurate diagnosis.

Normal readings

Example of a Type A tympanogram

Normal readings, i.e. Type A tympanogram, can be identified by a mountain-shaped graph that peaks around the 0 daPa mark. The pressure inside the middle ear usually ranges from -100 to +100 daPa.

These readings indicate that:

  • The eardrums and ossicles (small bones found in the middle ear) move normally in response to the stimuli
  • Pressure in the middle ear is normal
  • There’s no fluid in the middle ear

Other tympanogram readings

Other tympanogram readings include Type AS, Type AD, Type B and Type C.

Type AS (shallow)

Example of a Type As tympanogram

Type AS tympanograms have a lower maximum height than that of Type A curves, indicating low compliance and a stiff middle ear system. It requires further investigation to determine if there is a middle ear condition.

Possible middle ear conditions that can cause a shallow tympanogram include myringosclerosis (scarring of the eardrum) and otosclerosis (hardening of the middle ear bones).

Type AD (deep)

Example of a Type Ad tympanogram

Type AD tympanograms have a high maximum height, indicating high compliance and a hypermobile eardrum. Similar to Type AS, further investigation is required to rule out middle ear conditions such as ossicular chain discontinuity.

Type B

Example of a Type B tympanogram

Type B tympanograms feature a flat line with a normal ear canal volume. Common causes of such tympanograms include OME and cholesteatoma (tumour in the middle ear).

A hole or tear in the eardrum can also cause a flat graph. However, in cases like this, the ear canal volume exceeds the normal range.

Type C

Example of a Type C tympanogram

Type C tympanograms have mountain-shaped curves that are skewed towards the left of the graph. This indicates a highly negative middle ear pressure, which often results in a retracted eardrum.

Common causes include upper respiratory illnesses, a developing or recovering ear infection or Eustachian tube dysfunction.

FAQs About Tympanometry and Tympanograms

What is the difference between tympanometry and audiometry?

Tympanometry assesses the integrity of the eardrum and the function of the middle ear whereas audiometry measures your hearing sensitivity across sound frequencies.

Tympanometry is often conducted to complement and check the consistency of the audiometric results when a conductive hearing loss is detected.

Who can take a tympanometry test?

Tympanometry is suitable for all ages, including newborns. If you’re keen on taking this test, book an appointment at Hearing Partners today.

How long does a tympanometry test take?

The test takes approximately 5 minutes to complete for both ears.

Does tympanometry hurt?

No, you will hear a tone and feel a slight sensation in the ear but it doesn’t hurt. However, if your eardrum is inflamed, you may experience some transient discomfort.

Are there risks associated with tympanometry?

No, there aren’t any risks associated with tympanometry. If you have enquiries regarding this test, get in touch with our hearing care professionals today.

What should I take note of when taking a tympanometry test?

When taking a tympanometry test, you’ll be advised to relax and avoid any movements including talking and swallowing saliva as they may cause the results to be inaccurate.

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