Impedance Audiometry Test: Complete Guide to Procedure, Results & Interpretation

Impedance audiometry is a crucial component of modern audiological evaluations, particularly in patients undergoing head and neck surgery . It provides essential, objective information about the status of the middle ear and parts of the central auditory system, including speech discrimination,  that other hearing tests cannot.

An impedance audiometry test is an objective examination that assesses the condition of the middle ear structures. It measures how well the tympanic membrane (eardrum) and the ossicles (the tiny bones of the middle ear) move in response to air pressure changes in the ear canal and contributes to the assessment of the speech discrimination score . This test does not directly measure hearing sensitivity but rather evaluates the mechanical function of the ear.

An impedance test, in this context, refers to measuring the opposition to the flow of acoustic energy. A healthy middle ear is designed to be low-impedance, meaning it efficiently transfers sound waves from the air-filled ear canal to the fluid-filled inner ear. High impedance suggests a blockage or stiffness in the middle ear system, impairing this transfer and potentially leading to hearing loss.

Impedance audiometry helps to examine the functionality of the middle ear that transmits the sound between the outside and the inside of the ear and its connection to the middle and inner ear . The test will demonstrate the work in the process of moving sound by the eardrum and the little bones that are found in the ear, including the malleus, incus, stapes, and stapedius muscle.

The primary objective of impedance audiometry is to identify issues which are not visible to the eye when one looks at the ear. It provides definite numbers regarding the movement of the eardrum, the amount of air pressure in the middle ear and the way the middle ear muscles respond to the sounds that you produce. Through these figures, an audiologist can determine whether the ear middle ear is normal or there is some issue such as fluid in the ear, low pressure, hearing loss, hole in the ear drum, stiff bones, or the need for hearing aids, impacting word recognition.

Audiometry and impedance audiometry are important tests to be able to check hearing and ear health, although they do different work, and measure different things. Audiometry is primarily a test of hearing ability in relation to various sounds of various pitches and strengths. 

It informs you of the extent of hearing loss that you have suffered and which form it is; conductive, sensorineural, or mixed. In this test, you are required to press a button or scream when you hear a tone.

Instead, impedance audiometry examines the mechanics and reflexes in the middle ear, but not how you hear. It evaluates the conduction of sound through the middle ear and the response of the eardrum and the tiny bones to the variations in air pressure and sound. 

The test is used in the detection of middle ear disorders such as ear fluid, tight eardrum, ear drum hole, or the malfunction of the small bones. It will also work with babies and young children or anyone who is incapable of cooperating because it will not require you to do so, thus allowing for the assessment of speech intelligibility .

These two tests complement each other. Audiometry informs you of the degree to which you can hear, and impedance audiometry informs you of the well being of the middle ear. By using both, doctors can determine whether the type of hearing loss is caused by the middle ear or inner ear and also they are able to identify the specific cause of the issue.

Tests that examine the functioning of the middle ear are impedance audiometry and tympanometry. They are very similar though they are not identical. An important component of the impedance audiometry is Tympanometry, especially in cases of noise trauma . Impedance audiometry incorporates a number of tests that test the responsiveness of the ear to sound and pressure, and tympanometry only examines the movement of the ear drum and the pressure of the air in the middle ear cavity.

To be simple, tympanometry is an element of impedance audiometry and it produces the most accurate test of the quality of sound transmission by the eardrum and the middle ear system. A soft tip of the probe is inserted into the ear canal bringing small variations on the air pressure. 

These alterations of pressure cause the eardrum to vibrate and the equipment measures the ease at which the movement occurs. This graph is referred to as a tympanogram and it indicates the presence of normal motion or presence of issues in the ear drum like fluid accumulation, obstruction of eardrum by eardrum tube, or stiffness in the small bones of the ear, and can be further analyzed using brainstem evoked response audiometry .

Tympanometry is a mechanical evaluation of the middle ear activity, whereas the entire impedance audiometry is representative of a complete evaluation, which includes both mechanical and reflexive response.

Impedance test, sometimes called impedance audiometry is a significant test which assists in determining the effectiveness of the conduction of sound to and through the middle ear. Its primary role is to assess the eardrum mobility, the pressure of the middle ear cavity and the reflex to sound stimuli of the middle ear muscles, as well as bone conduction . Through the analysis of these parameters, including bone conduction thresholds, the test assists a doctor in the differential diagnosis of the presence of blockages, fluid accumulation, or stiffness which could be influencing normal hearing within normal limits.

In contrast to the traditional hearing tests, the impedance audiometry is objective and is not dependent on the active participation of the patient. It is precise and dependable in a matter of minutes thereby being applicable to patients of all ages, infants and young children are included.

The impedance test is usually prescribed by doctors who suspect the presence of middle ear issues that cannot be observed in case of an ordinary ear check. It is usually recommended in the cases below, particularly when evaluating air conduction thresholds :

• In case a patient has hearing loss, fullness, or ear pressure.

• In case of an indication of recurring ear infections or the accumulation of fluid behind the ear drum.

• To test the work of the eardrums (the eardrums provide the ear with normal ear pressure).

• To observe the middle ear recovery or measure the post-surgical outcomes before or after ear surgery.

• When the outcomes of the audiometry suggest that the hearing loss is conductive and that additional examination is required.

• In the case of newborns and children, to identify early ear issues that could have an impact on the growth of speech and language.

Impedance audiometry test is useful in the diagnosis of many disorders of the middle ear including:

• Middle Ear Fluid (Otitis Media with Effusion): Refers to the presence of fluid behind the eardrum, which in most cases leads to the hearing being muffled or the ear filling.

• Eustachian Tube Dysfunction: This occurs when the tube that connects the middle ear with the throat is not opening properly and as a result, this brings about an imbalance in the pressure and discomfort.

• Perforated Eardrum: The test is able to detect the abnormal movement of the eardrum which can indicate the presence of a hole or tear in the eardrum.

• Ossicular Chain Problems: Discovers stiffness or discontinuity in the small bones (malleus, incus, and stapes) that transmit sound.

Negative Middle Ear Pressure: Indicates the initial infection or congestion of the ear caused by sinus.

Importance The study demonstrates that children with frequent ear infections have a high risk of developing hearing impairment (DeShazer, 2018).<|human|>1.Significance of the Children with Recurrent Ear Infections The study reveals that children with frequent ear infections are at high risk of hearing impairment (DeShazer, 2018).

The impaired audiometry is particularly effective with children who frequently have ear infections or have hearing issues. Since children might not complain of what is wrong, this is a painless, non-invasive test that can detect concealed ear problems, including potential hearing problems,  at an early stage.

It assists pediatricians and audiologists:

• Detect the presence of fluid that may cause hearing and speech development.

• Follow-up chronic otitis media (persistent middle ear infections).

• Establish the necessity of ear tubes (grommets) or other medical procedures.

• Monitor ear infection or surgery progression.

Problems that are prevented by early diagnosis using impedance testing include delayed speech, poor school performance, and deafness in the long run.

Findings of tympanometry are displayed in a graph referred to as tympanogram. The nature of the problem is indicated by the shape of the curve.

Characteristics of Type B tympanogram

A type B tympanogram is a flat line with no discernible peak. This indicates that the tympanic membrane is not moving, regardless of the air pressure applied in the ear canal.

Clinical significance and interpretation

This result is highly suggestive of fluid in the middle ear (otitis media), a perforation of the eardrum, or a blockage of the probe tip. The audiologist will use the ear canal volume measurement to differentiate: a normal ear canal volume with a flat tympanogram points to otitis media, while a very large volume suggests a perforation.

Associated ear conditions

The primary condition associated is otitis media with effusion. It can also be seen in cases of cholesteatoma or significant scarring of the middle ear.

Treatment implications

A type B tympanogram often requires medical referral to an ENT doctor for management of the underlying middle ear condition, especially in children with persistent otitis media.

Features of Type C tympanogram

A Type C tympanogram shows a clear peak, but the peak is shifted to the left, indicating significant negative pressure in the middle ear space (typically beyond -150 daPa).

What Type C results indicate

This result is a classic sign of eustachian tube dysfunction. The eustachian tube, which connects the middle ear to the back of the throat, is not opening properly to equalize pressure. This vacuum can lead to fluid being drawn into the middle ear cavity.

Relationship to eustachian tube function

It directly demonstrates poor eustachian tube function. This can be a precursor to developing otitis media.

Follow-up recommendations

Monitoring or medical management to improve eustachian tube function may be recommended. This is a common finding in individuals with colds or sinus issues.

A Type A tympanogram has a distinct peak centered around 0 daPa (normal atmospheric pressure), indicating normal middle ear pressure and mobility. This is the expected result in a healthy ear.

Type A variations (As, Ad)

• Type As: The 's' stands for stiff. The peak is at the correct pressure (0 daPa), but it is very shallow. This suggests stiffness in the middle ear system, often seen in the early stages of otosclerosis. Static compliance is low.

• Type Ad: The 'd' stands for deep or disarticulated. The peak is extremely high, often off the chart. This indicates a hypermobile or flaccid tympanic membrane, often caused by a break in the ossicular chain (ossicular discontinuity) or a healed perforation.

Abnormal patterns and their meanings

Other, rarer patterns like a Type D (W-shaped) can indicate specific middle ear diseases. Each tympanometric curve provides a unique diagnostic clue about middle ear function.

The whole process of an impedance audiometry test is quick, painless, and highly informative.

Patient preparation requirements

Generally, no special preparation is needed. Patients should inform the audiologist about any current ear pain, discharge, or recent history of ear infections.

Ear examination before testing

The audiologist will first perform an otoscopy, a visual examination of the ear canal and tympanic membrane, using an otoscope. This is to ensure the ear canal is clear of excessive wax or foreign objects and that there isn't a visible perforation that would contraindicate the test.

Conditions that may affect results

A blocked ear canal (due to wax or debris), a crying or moving patient, or a perforation in the eardrum can significantly affect the results of the impedance testing.

Safety considerations

The test is extremely safe. The pressure changes are minimal and brief. The loud sound used for reflex testing is well within safe exposure limits and is presented for only a second or two.

Equipment setup and calibration

The impedance audiometer is calibrated daily to ensure accuracy. The audiologist selects the appropriate-sized tip for the small probe.

Probe insertion and sealing

A small probe with a soft tip is placed into the opening of the ear canal, creating an airtight seal. The patient will feel the probe tip, similar to an earplug. This is done for the left ear and right ear separately.

Tympanometry measurements

The machine automatically varies the pressure in the ear canal from positive to negative. While this happens, a low-frequency pure tone is presented, and the machine measures how much sound is reflected back, assessing the eardrum's movement.

Acoustic reflex testing

Next, a series of short, loud sounds are presented through the probe to test the stapedial reflex. The machine detects the tiny change in impedance when the middle ear muscles contract.

Duration and patient experience

The entire test for both ears usually takes less than five minutes. It is a core part of the audiological assessment.

Sensations patients may experience

Patients will feel a slight change in ear pressure, similar to ascending or descending in an elevator. They will hear the low humming tone during tympanometry and the louder beeps during reflex testing.

Sounds and pressure changes

The sound levels and pressure are carefully controlled. Any discomfort is momentary. The test provides crucial data about middle ear function.

Comfort level and safety measures

The test is generally comfortable. The audiologist will explain each step to ensure the patient is at ease. The airtight seal is crucial for accurate impedance measurements.

Post-test procedures

There are no post-test restrictions. The audiologist will immediately have the results and can discuss them.

Understanding the report is key for both the professional and the patient.

Impedance audiometry test report components

A typical report will include the patient's information, the results for the left ear and right ear, and separate sections for tympanometry and acoustic reflexes.

Key measurements and their meanings

The report will list the numerical values for ear canal volume, compliance, and middle ear pressure.

Graphical representations

The tympanograms for each ear will be graphically presented, allowing for a quick visual assessment of the results.

Statistical data presentation

Acoustic reflex thresholds will be listed in a table, showing the decibel level at which the reflex was triggered for each tested frequency.

Normal hearing function indicators

A Type A tympanogram with reflexes present at normal levels indicates healthy middle ear function.

Mild to severe abnormalities

Deviations from Type A, such as Type C or As, indicate mild to moderate abnormalities. A Type B tympanogram indicates a more significant issue.

Patterns suggesting specific conditions

The distinct patterns (A, B, C, As, Ad) are strongly correlated with specific middle ear conditions.

Recommendations based on results

The report will conclude with an interpretation and recommendations, such as "suggestive of middle ear effusion; recommend medical follow-up."

Professional vs. patient understanding

An audiologist interprets the results within a complex diagnostic framework. For a patient, the focus is on understanding what the results mean for their hearing health and what the next steps are.

When to seek clarification

Patients should always ask for clarification if they don't understand the terminology or the implications for their treatment.

Follow-up testing recommendations

Based on the results, the audiologist might recommend further hearing tests, medical consultation, or a re-test in a few weeks.

Treatment planning based on results

The results directly influence treatment. A Type B tympanogram may lead to a prescription for antibiotics or the insertion of PE tubes, while a Type As may lead to imaging to investigate for otosclerosis. This objective test is vital for planning.

Tympanometry is predominantly employed to determine whether the middle ear pressure and the movement of the ear drum is normal. It assists in detecting ear infections, fluid accumulation (otitis media with effusion), holes in the ear drum or issues with the eustachian tube.

The extra of what impaired audiometry does is that it also assesses the acoustic reflex which examines the nerve path between the ear and the brainstem. This reflex serves as the defense mechanism of the ear against high levels of sound and indicates whether hearing and facial nerves are functional or not, often assessed using a device called an audiometer.

Tympanometry measures:

• Eardrum compliance (ability to move)

• Middle ear pressure

• Ear canal volume

• Type of tympanogram curve (A, B, C types which represent various ear states)

Audiometry Impedance Audiometry: Measures all of the above and:

• Acoustic Reflex Thresholds- the minimum sound level that causes the stapedius muscle reflex.

• Reflex Decay- tests the duration of the reflex (assists in identifying nerve issues or retrocochlear problems)

Routine screening of middle ear health is commonly done using Tympanometry to detect middle ear infections or middle ear pressure issues, particularly in children.

The impedance Audiometry is employed in detailed diagnosis, including eustachian tube function test which is applicable in the cases of unexplainable air conduction hearing loss, retrocochlear disorders, problems of the facial nerve, or at the time of ear surgery and after surgery.

Comparison Table: Impedance Audiometry vs Tympanometry

Impedance audiometry test is a hearing test that is very accessible and relatively cheap in India. It provides valuable data on the operation of the middle ear, and assists the physician in locating issues, such as fluid in the ear, eardrum holes, and/or, eardrum problems, helping to determine if they fall within the normal range.

Average Test Price Range 

Impedance audiometry test is typically priced between 500INR and 1500 INR in India. 

• It can vary depending upon the city, the nature of healthcare facility, and experience of audiologist.

• Small cities or government hospitals: ₹500 -800. 

• At home clinics or diagnostics centers: 800-1200 INR. 

• In freedom ENT hospitals with multispecialty or premium hospitals: 1200 -1500 or higher. 

This renders the test inexpensive and simple to acquire among adults and children who require a comprehensive test of the ear middle ear.

The costs of the impedance audiometry test in India are influenced by a number of factors: 

• Type of Healthcare Facility 

• Equipment and Technology Used. 

• Audiologist’s Expertise 

• Other Tests or Package Offers. 

The impedance audiometry test is a good and non-invasive method of the individual to assess the functionality of the middle ear. It assists the doctor in making a correct diagnosis of ear fluid, ear eardrum holes, eardrum issues as well as the ear fluid and clogging of the eardrum by measuring the motion of the eardrum, the middle ear pressure and the reflex response. 

It is a very important device both to the adults and kids and particularly those who have got recurrent ear infections or those who have no explanation as to why they have hearing issues. The test is fast, painless and highly reliable; hence it is acceptable in routine hearing test and evaluation of treatment advancement.

**Medical Disclaimer  - The following information is for educational purposes only. No information provided on this website, including text, graphic, and images, are intended as substitutes for professional medical advice. Please consult with your doctor about specific medical advice pertaining to your condition(s).