Tympanometry

Key takeaways

Tympanometry belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tympanometry to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tympanometry from memory before moving on to harder problems.

Reference excerpt

Tympanometry is an acoustic evaluation of the condition of the middle ear eardrum (tympanic membrane) and the conduction bones by creating variations of air pressure in the ear canal. Tympanometry is an objective test of middle-ear function. It is not a hearing test, but rather a measure of energy transmission through the middle ear. It is not a measure of eardrum or middle ear mobility. It is an acoustic measure, measured by a microphone, as part of the ear canal probe, inserted into the ear canal. The test should not be used to assess the sensitivity of hearing and the results of this test should always be viewed in conjunction with pure tone audiometry. Tympanometry is a valuable component of the audiometric evaluation. In evaluating hearing loss, tympanometry permits a distinction between sensorineural and conductive hearing loss, when evaluation is not apparent via Weber and Rinne testing. Furthermore, in a primary care setting, tympanometry can be helpful in making the diagnosis of otitis media by demonstrating the presence of fluid build up in the middle ear cavity.

Operation A tone of 226 Hz is generated by a probe tip inserted into the external ear canal, where the sound strikes the tympanic membrane, causing vibration of the middle ear. While 226 Hz is the most common probe tone, others can be used. In infants under 4 months of age, research has shown a 1000 Hz tone yields more accurate results. Multi-frequency tympanometry is conducted at multiple frequencies between 250 and 2000 Hz and is used to help identify ossicular abnormalities. Admittance is how energy is transmitted through the middle ear. The instrument measures the reflected sound and expresses it as an admittance or compliance, plotting the results on a chart known as a tympanogram. Normally, the air pressure in the ear canal is the same as ambient pressure. Also, under normal conditions, the air pressure in the middle ear is approximately the same as ambient pressure since the eustachian tube opens periodically to ventilate the middle ear and equalize pressure. In a healthy individual, the maximum sound is transmitted through the middle ear when the ambient air pressure in the ear canal is equal to the pressure in the middle ear.

Procedure

After otoscopy (examination of the ear with an otoscope) to ensure that the path to the eardrum is clear and there is no perforation, the test is performed by inserting the tympanometer probe in the ear canal. The instrument changes the pressure in the ear, generates a pure tone, and measures the eardrum responses to the sound at different pressures. This produces a series of data measuring how admittance varies with pressure, which is plotted as a tympanogram:

Tympanograms are categorized according to the shape of the plot. A normal tympanogram (left) is labelled Type A. There is a normal pressure in the middle ear with normal mobility of the eardrum and ossicles. Type B tympanogram may reveal (a) fluid in the middle ear, (b) perforation of the tympanic membrane or patent pressure equalization tube, or (c) a tumor in the middle ear. Type C tympanograms are consistent with negative pressure in the middle ear space resulting from compromised eustachian tube function and a retracted tympanic membrane. The categorising of tympanometric data should not be used as a diagnostic indicator. It is merely a description of shape. There is a distinction between the three types as well as the two subtypes of type A, namely AS and AD. For example, AS (a shallow tympanogram) will show a stiff middle ear system or AD (a deep tympanogram) consistent with ossicular discontinuity or a monomeric membrane. Only measures of static acoustic admittance, ear canal volume, and tympanometric width/gradient compared to sex, age, and race specific normative data can be used to somewhat accurately diagnose middle ear pathology along with the use of other audiometric data (e.g. air and bone conduction thresholds, otoscopic examination, normal word recognition at elevated presentation levels, etc.).

Tympanometry by end users

Smartphones There have been a few efforts to lower the cost of tympanometers by using smartphones. In 2022, University of Washington researchers had demonstrated an end-to-end smartphone-based tympanometer system that consists of a portable phone attachment used to change the air pressure in the ear. The smartphone computes and displays a tympanogram and reports peak acoustic admittance in real-time. The smartphone-based system operated at 226 Hz and in proof-of-concept testing showed comparable results to commercial tympanometers. Given the ubiquity of smartphones across the world, these mobile systems may help make these audiology tools accessible across the world.

Consumer devices Consumer devices have been made to allow checking for middle-ear fluid at home. A 2009 study found the Ear Check Middle Ear Monitor consumer model acoustic reflectometer to give few false negative results in detecting middle-ear fluid; specificity and positive predictive values were modest, with many false positives. The device was no longer available in 2023.

References

External links Medscape article by Kathleen C M Campbel Basic Multifrequency Tympanometry: The Physical Background

Illustrations

Worked examples

Example 1 — a first encounter with Tympanometry

Start with the simplest possible case. Write down what Tympanometry claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tympanometry before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tympanometry ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tympanometry

In research: Tympanometry appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tympanometry in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tympanometry is common in secondary-school and first-year university syllabi. It links to neighbouring topics Audiology, Ear procedures, Medical tests, so understanding it makes those chapters shorter.
In everyday life: Look for Tympanometry outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Tympanometry in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tympanometry means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Tympanometry out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tympanometry in simple terms?

Tympanometry is an acoustic evaluation of the condition of the middle ear eardrum (tympanic membrane) and the conduction bones by creating variations of air pressure in the ear canal. Tympanometry is an objective test of middle-ear function.

Why does Tympanometry matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tympanometry?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tympanometry.