Tympanometry

What Is Tympanometry?

Tympanometry is a quick, objective diagnostic test that measures how well the eardrum (tympanic membrane) and middle ear are functioning. It does this by assessing the eardrum`s compliance — its ability to move freely in response to changes in air pressure — and by measuring the pressure within the middle ear space. The result is a graph called a tympanogram, which provides the audiologist with valuable clinical information about the health and mechanical function of the middle ear system.

Unlike a standard hearing test (pure tone audiometry), which requires you to listen for tones and press a button, tympanometry is an entirely objective measurement. It does not depend on the patient`s active cooperation or response, which makes it particularly valuable for testing young children, infants, people with learning difficulties, and anyone who cannot reliably perform behavioural audiometry. This objectivity is one of the reasons tympanometry has become one of the most widely used tests in audiology clinics across the UK — both NHS and private.

Tympanometry is not a hearing test in the conventional sense. It does not measure how well you can hear sounds. Instead, it measures the mechanical properties of the middle ear — the system of structures that transmits sound from the eardrum to the inner ear. When the middle ear is not functioning properly, sound transmission is impaired and hearing loss results. Tympanometry identifies the cause of that impairment, complementing the hearing thresholds obtained through audiometry and the inner ear assessment provided by bone conduction testing.

How Does Tympanometry Work?

The tympanometry procedure is straightforward, fast, and entirely painless. Understanding the underlying principle helps explain what the results mean.

The instrument and probe

The audiologist uses a tympanometer — a small, handheld or desktop instrument fitted with a probe that has three channels:

• A loudspeaker channel that delivers a continuous low-frequency tone (usually 226 Hz for adults and older children, or 1000 Hz for infants under approximately six months)
• A microphone channel that measures the sound reflected back from the eardrum
• An air pump channel that systematically varies the air pressure in the ear canal from positive to negative (typically from +200 to -400 decapascals, or daPa)

The procedure

The audiologist selects a soft rubber or foam probe tip of appropriate size and gently inserts it into the opening of your ear canal, creating an airtight seal. Once the seal is achieved, the instrument automatically plays the tone, varies the pressure, and records the measurements. The entire process takes approximately 15 to 30 seconds per ear — often less.

What you feel

You will feel a slight sensation of pressure change in your ear, similar to the feeling you experience during take-off or landing in an aircraft, or when driving through a tunnel. Some people describe a brief feeling of fullness or a quiet humming tone. There is no pain and no discomfort. You do not need to do anything — just sit still and avoid swallowing, speaking, or chewing during the few seconds the measurement takes, as jaw movements can affect the seal and the reading.

The underlying physics

The principle behind tympanometry is straightforward. When a sound wave hits the eardrum, some of the energy is transmitted through the eardrum into the middle ear (this is useful hearing), and some is reflected back. The proportion of energy reflected versus transmitted depends on the stiffness and mobility of the eardrum and middle ear system. A healthy, normally functioning eardrum is most mobile (most compliant) when the air pressure on both sides of the membrane is equal. By systematically sweeping the pressure in the ear canal and measuring the reflected sound at each pressure, the tympanometer identifies the pressure at which the eardrum is most compliant — and plots this as the peak of the tympanogram.

Interpreting the Tympanogram — Types A, B, and C

The tympanogram is a graph with pressure (in daPa) on the horizontal axis and compliance (admittance, in millilitres or millimhos) on the vertical axis. The shape, height, and position of the peak — or the absence of a peak — tells the audiologist a great deal about middle ear function. The Jerger classification system, developed by audiologist James Jerger in 1970 and still universally used today, categorises tympanograms into several types:

Type A — Normal

A Type A tympanogram shows a clear, well-defined peak centred at or near 0 daPa (atmospheric pressure), with normal compliance. This indicates that the eardrum is moving freely, the middle ear pressure is normal, and the ossicular chain (the three tiny bones of the middle ear) is functioning properly. A Type A result is the expected finding in a healthy ear.

Two important subtypes exist:

• Type As (shallow): A Type A pattern with a reduced peak height (lower compliance). The `s` stands for `shallow` or `stiff.` This pattern suggests increased stiffness of the middle ear system, which can be caused by otosclerosis (abnormal bone fixation of the stapes), thickening or scarring of the eardrum (tympanosclerosis), or early fluid accumulation in the middle ear. Otosclerosis is one of the most important conditions identified by a Type As pattern.
• Type Ad (deep): A Type A pattern with an abnormally tall, peaked compliance value. The `d` stands for `deep` or `disarticulated.` This pattern suggests excessive eardrum mobility, which can be caused by a flaccid or atrophic eardrum (thinned by previous perforation or infection), or by ossicular chain discontinuity — a break in the chain of middle ear bones, typically resulting from chronic infection or head trauma. A very tall, narrow peak with low-frequency oscillation is characteristic of ossicular disruption.

Type B — Flat

A Type B tympanogram is flat, showing no discernible peak at any pressure. This is a clinically significant finding with three main causes:

• Glue ear (otitis media with effusion): By far the most common cause, especially in children. When the middle ear space is filled with thick, viscous fluid, the eardrum cannot move and compliance is minimal at all pressures. The National Deaf Children`s Society (NDCS) estimates that 8 out of 10 children will experience at least one episode of glue ear by the age of 10, making tympanometry an essential tool in paediatric audiology
• Eardrum perforation: If there is a hole in the eardrum, the air pressure in the ear canal and middle ear equalises through the perforation, and the tympanometer records a flat trace with an unusually large ear canal volume (because the probe is effectively measuring the combined volume of the ear canal and the middle ear space). This large-volume flat pattern is diagnostically distinct from the normal-volume flat pattern of glue ear
• Blocked probe or occluding ear wax: If the probe tip is blocked by wax or is pushed against the ear canal wall, a flat trace with an unusually small canal volume is recorded. The audiologist recognises this artefact and repositions or clears the probe

Type C — Negative pressure

A Type C tympanogram shows a peak that is shifted towards negative pressure (typically beyond -100 daPa). This indicates that the pressure in the middle ear is lower than atmospheric pressure, which is the hallmark of Eustachian tube dysfunction. The Eustachian tube connects the middle ear to the back of the throat (nasopharynx) and is responsible for ventilating the middle ear and equalising pressure. When the tube is not opening properly — due to upper respiratory infection, allergies, adenoid enlargement, or anatomical factors — air in the middle ear is gradually absorbed by the mucosal lining, creating negative pressure that retracts the eardrum inward. A Type C tympanogram may represent an early stage in the development of glue ear, as persistent Eustachian tube dysfunction often leads to fluid accumulation over time.

Tympanometry in Paediatric Assessment

Tympanometry is one of the most important diagnostic tools in paediatric audiology. Glue ear is extremely prevalent in young children — the NICE guideline on otitis media with effusion in under 12s (NG233) notes that glue ear is one of the most common childhood conditions, with peak prevalence around age two to five. Because glue ear can cause significant conductive hearing loss that affects speech, language, and learning, early and accurate diagnosis is essential.

Tympanometry is ideally suited to paediatric use for several reasons:

• No cooperation required: The child does not need to respond to sounds, follow instructions, or sit in a soundproofed booth. The test is purely objective
• Speed: The measurement takes seconds, which is critical when working with young, restless children
• Comfort: The test is painless and well tolerated, even by infants (using a 1000 Hz probe tone for babies under six months)
• Monitoring: Serial tympanometry allows audiologists and ENT surgeons to track the course of glue ear over weeks and months, informing decisions about whether to adopt a `watchful waiting` approach or proceed with grommet (ventilation tube) insertion
• Pre- and post-grommet assessment: Tympanometry confirms whether grommets are in situ and patent (functioning), and detects when they have extruded

In the context of children`s hearing tests, tympanometry is routinely performed alongside pure tone audiometry (for children old enough to cooperate) or visual reinforcement audiometry (for younger children), providing a comprehensive picture of both middle ear function and hearing sensitivity.

Acoustic Reflex Testing

Most modern tympanometers also include the capability to test the acoustic reflex (also called the stapedial reflex or middle ear muscle reflex). This is a closely related but distinct measurement that is often performed immediately after tympanometry.

What is the acoustic reflex?

The acoustic reflex is a protective mechanism. When a loud sound (typically 70–100 dB above hearing threshold) reaches the cochlea, a neural reflex arc through the brainstem triggers contraction of the stapedius muscle in the middle ear. This tiny muscle stiffens the ossicular chain, reducing the amount of sound energy transmitted to the cochlea and protecting the delicate hair cells from damage. The reflex is bilateral — stimulating one ear produces a muscle contraction in both ears.

How it is measured

The tympanometer presents loud tones at specific frequencies (typically 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz) through the probe while monitoring the compliance of the eardrum. When the stapedius muscle contracts, it stiffens the eardrum slightly, producing a measurable change in compliance that the instrument detects. The audiologist records the acoustic reflex threshold — the lowest intensity at which the reflex is triggered — for each frequency and each ear.

Clinical significance

Acoustic reflex testing provides additional diagnostic information beyond tympanometry alone:

• Absent reflexes with a Type B tympanogram: Consistent with glue ear or middle ear pathology preventing the reflex from being detected
• Absent or elevated reflexes with a Type A tympanogram: May suggest otosclerosis (the stapes is fixed and cannot be stiffened further), significant sensorineural hearing loss (the cochlea is too damaged to trigger the reflex), or a retrocochlear lesion such as acoustic neuroma (affecting the neural pathway)
• Acoustic reflex decay: A sustained reflex that fades rapidly may indicate a retrocochlear pathology and warrants further investigation, potentially including auditory brainstem response testing or MRI

Conditions Detected by Tympanometry

Tympanometry is valuable in diagnosing and monitoring a wide range of middle ear conditions:

• Glue ear (otitis media with effusion): The most common indication, particularly in children. A Type B tympanogram with normal ear canal volume is the classic finding
• Acute otitis media: Middle ear infection with inflammation and possible fluid. Tympanometry may show a Type B or Type C pattern depending on the stage
• Eardrum perforation: A Type B tympanogram with a large ear canal volume indicates a perforation. This finding is important before ear wax removal by irrigation, as irrigation through a perforated eardrum risks introducing water and bacteria into the middle ear
• Otosclerosis: A Type As (shallow) tympanogram with absent or elevated acoustic reflexes is suggestive of otosclerosis, particularly in adults with progressive conductive hearing loss
• Ossicular chain discontinuity: A Type Ad (deep) tympanogram with absent acoustic reflexes suggests a break in the chain of middle ear bones
• Eustachian tube dysfunction: A Type C tympanogram indicates negative middle ear pressure due to poor Eustachian tube ventilation. This is common during and after upper respiratory infections and in children with enlarged adenoids
• Tympanosclerosis: Scarring and calcification of the eardrum or middle ear structures, which may produce a Type As pattern
• Cholesteatoma: An abnormal growth of skin cells in the middle ear, which may be associated with eardrum retraction, perforation, or abnormal tympanometry findings

Tympanometry and Its Relationship to Hearing Tests

Tympanometry is not a replacement for a hearing test — it is a complement to one. While audiometry tells you how much hearing loss is present and at which frequencies, tympanometry tells you why the hearing loss may be present by assessing the mechanical function of the middle ear. When combined with bone conduction testing, which isolates inner ear function, tympanometry completes the diagnostic picture.

For example, consider a patient whose audiogram shows a mild conductive hearing loss in one ear. Bone conduction testing confirms that the inner ear is normal. Tympanometry then reveals a Type B trace with normal canal volume — glue ear. The diagnosis is clear, and the management pathway (watchful waiting, or referral for grommets if persistent) follows logically. Without tympanometry, the audiologist would know that there was a conductive loss but could not confirm the specific cause without further investigation.

NHS Availability and Where to Get Tympanometry

Tympanometry is widely available across the UK, both on the NHS and in private audiology clinics. It is a routine component of audiological assessment at NHS audiology departments, paediatric audiology services, and ENT clinics. Most private audiology providers — including Boots Hearingcare, Specsavers Audiology, and Hidden Hearing — include tympanometry as part of their comprehensive hearing assessment at no additional cost.

You do not usually need to request tympanometry specifically. Your audiologist will include it whenever middle ear function needs to be assessed — which is the case in most diagnostic hearing assessments, particularly those involving suspected conductive hearing loss, glue ear in children, pre-ear wax removal safety checks, or monitoring of known middle ear conditions. If you are referred by your GP or ENT consultant for a hearing assessment, tympanometry will typically be part of the test battery.

Use our search tool to find audiologists near you who offer comprehensive hearing assessments including tympanometry. Whether you are concerned about your own hearing, investigating your child`s hearing, or need a pre-treatment safety check, tympanometry provides fast, painless, objective answers about the health of your middle ear — and those answers are essential for getting the right diagnosis and the right treatment.