01Purpose and principlesWhat the assessment is for and the core concepts behind it.
Audiometry and tympanometry answer different questions and are most useful when their findings are brought together. Pure-tone audiometry estimates the quietest tones a person can reliably detect at selected frequencies. Tympanometry examines how the ear transmits a probe tone while canal pressure changes. A mechanically normal middle ear can coexist with substantial cochlear hearing loss, and an abnormal mechanical result does not by itself quantify the person's hearing disability.
An audiogram places frequency on the horizontal axis and hearing level in decibels on the vertical axis. Higher numerical dB HL thresholds mean that more intense sound was required for detection. Air-conduction testing evaluates the complete external, middle and inner-ear pathway, whereas bone-conduction testing helps separate transmission loss from impaired cochlear or neural sensitivity. Read the actual symbols and legend because the chart also indicates masking, transducer use and responses that could not be obtained at the equipment limit.
Threshold measurement depends on cooperation, calibration, ambient noise and clear instructions. The person should understand that they respond to a tone, however faint, rather than guess according to a predictable rhythm. The examiner varies the timing, confirms the task has been understood and adapts the assessment to communication or attention needs. A smaller set of reliable measurements can be more informative than a full chart assembled from inconsistent responses.
A tympanometer needs an appropriate seal and an unobstructed probe. It estimates admittance across a pressure sweep, identifies a peak when present and provides an equivalent canal-volume estimate. The peak pressure often approximates middle-ear pressure, but a flat trace has no measurable peak from which to infer it. These quantities reflect a physical system that changes with age, surgery and disease; they must be interpreted in the context of the examination rather than as independent diagnostic labels.
Key points
- Pure-tone audiometry measures frequency-specific behavioural hearing thresholds; tympanometry measures the mechanical response of the ear to changing pressure.
- Interpret air and bone thresholds with masking and reliability information before assigning a conductive, sensorineural or mixed mechanism.
- BSA threshold testing uses a 10 dB decrease after a response and 5 dB ascending steps to establish a reproducible threshold.
- Use a 226 Hz tympanometry probe from six months corrected age and a 1000 Hz probe below that age.
- A flat trace may reflect effusion, probe obstruction, perforation or a patent grommet; the canal-volume estimate and otoscopy help distinguish them.
- Describe tympanometric pressure, admittance, canal volume and trace quality; a letter classification alone is insufficient.
02Indications, selection and cautionsWhen it is useful, when urgency changes and important limitations.
Air thresholds poorer than valid bone thresholds indicate an air-bone gap. A normal bone line with a gap supports predominantly conductive loss, whereas elevated bone thresholds plus an additional gap support a mixed deficit. Confirm that masking was adequate before treating the bone responses as belonging to the ear being assessed.
Similarly elevated air and bone thresholds without a relevant gap suggest sensorineural impairment. Consider configuration, symmetry, onset and the person's listening difficulties. A gradual bilateral pattern may support age-related loss, but an unexplained asymmetry or abrupt change requires a different diagnostic approach.
An unexpectedly small canal-volume estimate suggests probe occlusion or contact with the canal wall. A flat trace with a plausible canal volume may support effusion. An unusually large estimate, particularly compared with the other ear, can indicate an open perforation or patent ventilation tube when the membrane was not clearly visible.
A shifted peak towards negative pressure can support Eustachian-tube dysfunction, but negative pressure alone does not prove fluid. A shallow or unusually mobile peak needs correlation with the membrane, ossicular history and hearing findings. Simple type A, B or C terminology should be supplemented by measurements and a descriptive interpretation.
03Method and interpretationA systematic approach to the test and its findings.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Preparation and otoscopyFirst step - Why
- Establish whether the chosen test is appropriate and identify factors that could invalidate it.
- Interpretation and limitations
- Review symptoms, previous results, noise exposure and surgery. Examine the canal and drum before inserting a probe or transducer. Tympanometry should not be performed on a discharging ear or a visibly red bulging drum; an obvious perforation already seen on otoscopy does not need pressure testing to demonstrate it.
- 02
Air- and bone-conduction threshold measurement - Why
- Determine reproducible sensitivity at relevant frequencies.
- Interpretation and limitations
- BSA uses 10 dB descending and 5 dB ascending steps. The threshold is the lowest level with responses in at least half the ascending trials and at least two responses at that level. In the first ear, repeat 1000 Hz; a discrepancy greater than 5 dB requires investigation rather than simple averaging.
- 03
Masking when cross-hearing is possible - Why
- Prevent the non-test cochlea from supplying an apparently better threshold.
- Interpretation and limitations
- Bone vibration can stimulate either cochlea, and sufficiently loud air-conducted sound can cross the skull. A trained audiologist applies masking according to transducer, threshold and air-bone relationships. If a reliable masked threshold cannot be established, report that limitation rather than implying that an ambiguous response is ear-specific.
- 04
Age-appropriate tympanometry - Why
- Assess middle-ear mechanical function using an appropriate probe frequency.
- Interpretation and limitations
- The March 2026 BSA procedure specifies 226 Hz from six months corrected age and 1000 Hz below six months. Infant high-frequency traces require their own interpretation; adult canal-volume and compliance assumptions should not be transferred to them. Artefact or an inadequate seal may require careful repeat testing.
- 05
Directed assessment beyond these tests - Why
- Resolve questions not answered by tone sensitivity or middle-ear mechanics.
- Interpretation and limitations
- Speech assessment, suitable paediatric methods and other audiological investigations may be needed when routine behavioural testing is limited. For adults with localising signs suggesting a vestibular schwannoma or cerebellopontine-angle lesion, NICE advises offering internal-auditory-meatus MRI regardless of pure-tone thresholds.
04Clinical next stepsHow the result changes management or prompts escalation.
01Reading a completed audiogramCheck validity before classifying the lossFirst stepA chart is available for a patient with hearing difficulty.+
- 1Confirm patient, side, test date, units, transducers and reliability notes; identify masked results and any no-response symbols.
- 2Compare air with bone by frequency, then compare ears, looking for a gap, raised sensory thresholds and asymmetry rather than relying on an average alone.
- 3Relate the findings to the clinical timeline and communication needs, arranging medical investigation where indicated and discussing rehabilitation even when a reversible lesion is absent.
02An abnormal or unexpected tympanogramCombine the trace with canal volume and otoscopyThe result is flat, markedly shifted or inconsistent with the examination.+
- 1Check the seal, probe position, canal obstruction and whether a repeat trace is safe and technically justified.
- 2Interpret a flat result using the canal-volume estimate and membrane findings; document when peak pressure cannot be measured.
- 3Refer or arrange follow-up according to the underlying clinical concern, including persistent adult effusion or another abnormal membrane finding, rather than treating a curve label in isolation.
03A test that should be deferred or adaptedProtect the ear and preserve the diagnostic planThere is discharge, painful acute middle-ear disease, recent surgery, a foreign body or unreliable cooperation.+
- 1Explain why the proposed test may be unsafe or uninterpretable and arrange assessment of the barrier or underlying disease.
- 2After reconstruction or ossicular procedures, obtain explicit medical advice; do not assume an ENT referral itself authorises tympanometry or early postoperative pressure testing.
- 3AlternativeUse an appropriate alternative assessment or reschedule with a clear purpose, while maintaining any urgent referral required by the presenting symptoms.
05Risks, monitoring and follow-upComplications, safety checks and further assessment.
- Record threshold reliability, masking limitations and the highest tested level when no response was obtained; lack of a response is not a measured threshold.
- Save the tympanometric trace with probe frequency, canal volume, peak pressure and admittance where measurable, and describe technical limitations.
- Compare serial audiograms with attention to test conditions and clinically meaningful changes rather than treating every 5 dB fluctuation as deterioration.
- Check hearing and middle-ear findings after treatment or resolution of a suspected transient conductive problem.
- Review communication goals alongside objective results, including speech in noise, warning sounds and the impact on work or education.
06Special situationsVariants, exceptions and circumstances that change the usual approach.
Average descriptors depend on their definition
The BSA adult audiometry document describes mild, moderate, severe and profound impairment using a five-frequency air-conduction average at 250, 500, 1000, 2000 and 4000 Hz: 21–40, 41–70, 71–95 and over 95 dB HL respectively. Other frameworks use different averages; specify the framework and retain the frequency-specific chart.
Felt vibration is not necessarily hearing
At sufficiently high levels, especially at low frequencies, a person may detect vibration rather than an auditory tone. The examiner should ask about the nature of the sensation and annotate possible vibrotactile responses. This matters when assessing severe or profound impairment and interpreting apparent residual bone sensitivity.
A curve letter is shorthand
The current BSA tympanometry procedure does not recommend relying on Jerger type classifications. If these familiar terms are used, add a plain description and the relevant measurements. Two flat traces can represent very different problems, and a peak at negative pressure cannot by itself settle whether an effusion is present.
Functional difficulty may remain underrepresented
A quiet-booth tone task does not reproduce a noisy ward, group conversation or a reverberant classroom. The audiogram can inform management without fully explaining listening effort. Ask about specific difficult settings and choose further assessment or support around those needs.
07Common pitfallsFrequent interpretation and management errors.
- 01
Diagnosing sensorineural normality from an unmasked bone line in a markedly asymmetric patient.
- 02
Calling every flat tympanogram effusion without checking the volume estimate and probe position.
- 03
Using an adult 226 Hz protocol for a baby below six months corrected age.
- 04
Performing pressure testing despite otorrhoea or assuming a recently operated ear is safe because an appointment was requested.
- 05
Using an average hearing descriptor as the sole criterion for whether someone needs hearing support.