Tuning Fork Tests — Rinne, Weber, and Absolute Bone Conduction

Tuning fork tests predate the audiometer by nearly a century. Heinrich Rinne described his test in 1855; Ernst Heinrich Weber, his in 1834. Despite the availability of pure-tone audiometry, these tests remain on every MBBS OSCE checklist and every ENT ward round — because they are fast, require no equipment beyond the fork itself, and provide a reliable bedside classification of hearing loss type when performed and interpreted correctly. They are also among the most commonly misperformed tests in clinical medicine.

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Which Tuning Fork to Use

The standard tuning fork for ENT assessment is 512 Hz. Reasons:

• 512 Hz is within the speech frequency range (500–3000 Hz) and therefore clinically relevant
• 256 Hz forks produce too much vibrotactile sensation — patients can “feel” the vibration through the skull, making interpretation unreliable (particularly in bone conduction testing)
• 1024 Hz forks decay too quickly for reliable sustained comparison testing

Some departments use 256 Hz for Rinne; if so, results must be interpreted with extra caution due to the vibrotactile issue. For absolute bone conduction (ABC) testing with Barany’s noise box, 256 Hz is acceptable.

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The Rinne Test

Principle

The Rinne test compares the patient’s air conduction (AC) threshold to their bone conduction (BC) threshold in the same ear — it determines whether air conduction is better than bone conduction (normal) or worse (indicating a conductive loss).

In a normal ear and in sensorineural hearing loss: AC > BC (Rinne positive — air is better than bone)

In conductive hearing loss of sufficient magnitude (approximately ≥20–25 dB): BC > AC (Rinne negative — bone is better than air)

Technique

1. Strike the tuning fork firmly against your knee or the hypothenar eminence (NOT on a desk — this produces overtones that distort the result). The fork should vibrate at its fundamental frequency, not ring or buzz.
2. Place the base of the fork (not the tines) firmly against the mastoid process (just behind the pinna), applying moderate pressure to ensure good bone contact. Ask the patient to tell you when they can no longer hear it.
3. Immediately when the patient indicates the sound has gone, transfer the fork — tines pointing toward the ear canal, approximately 2 cm away — and ask if they can hear it now.
4. Alternatively (and more reliable in practice): hold the tines 2 cm from the ear canal first and let the sound decay; then immediately place the base on the mastoid. Ask which is louder.

Interpretation

Rinne Positive (AC > BC): The patient hears the fork longer or louder by air than by bone. This is the normal result and is also seen in sensorineural hearing loss — in SNHL, both air and bone conduction are reduced proportionately, but AC remains better than BC.

Rinne Negative (BC > AC): The patient hears the fork longer or louder by bone than by air. This indicates conductive hearing loss — the middle ear mechanism is impaired, reducing air-conducted sound more than bone-conducted sound.

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The Critical Pitfall — False-Negative Rinne (The “Dead Ear”)

This is the most important and most frequently examined concept in tuning fork testing.

In a dead ear (severe to profound unilateral SNHL — cochlear function essentially absent on one side), the Rinne test gives a falsely negative result: the patient reports hearing the bone-conducted fork better than the air-conducted fork — which would normally indicate conductive hearing loss — but the reason is entirely different. The bone-conducted sound is being transcranially transmitted to the normal opposite cochlea. The patient is hearing the fork through their good ear, not through the tested ear at all. The sensorineural “dead” ear gives a false Rinne-negative result.

The clinical consequence: a patient with a dead ear on the right will have a Rinne-negative result on the right — which, without the Weber test, could be (incorrectly) interpreted as conductive hearing loss. This leads to entirely wrong management.

How to avoid this error: Never interpret the Rinne test without the Weber test. The Weber test will lateralise to the opposite (good) ear — which is the opposite of what you would expect in a true conductive loss (Weber lateralises to the worse/conductive ear). The combination resolves the ambiguity.

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The Weber Test

Principle

The Weber test assesses whether bone conduction is equal in both ears or lateralises to one side. It is a screening test of relative cochlear sensitivity — it tells you which ear receives the bone-conducted sound more strongly.

Technique

Strike the fork and place the base firmly on the midline of the skull — the vertex (top of the head) or the forehead (glabella) are both acceptable. Ask the patient: “Does the sound seem equal in both ears, or louder in one side? Point to where you hear it.”

Some examiners place the fork on the upper incisor teeth — dental bone contact provides excellent transmission, though it is uncomfortable for the patient and not universally acceptable.

Interpretation

Weber centralised (midline): Equal transmission to both cochleae — normal hearing or symmetric hearing loss.

Weber lateralises to the poorer hearing ear: Indicates conductive hearing loss on that side. The reason: in conductive loss, the middle ear is impaired but the cochlea is intact. The damaged middle ear “masks” less environmental noise (because less ambient sound reaches the cochlea through the impaired conductive pathway), and the bone-conducted tuning fork faces less competition from ambient sound in the conductive-loss ear. The effective signal-to-noise ratio is better in the conductive ear, so the sound appears louder on that side.

Weber lateralises to the better hearing ear: Indicates sensorineural hearing loss on the opposite (worse) side. The cochlea on the lateralised side is more sensitive; bone conduction reaches it more effectively. Sound appears louder in the better-functioning ear.

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Interpreting Rinne and Weber Together

flowchart TD
    A["Rinne + Weber"] --> B{"Affected-ear Rinne"}
    B -->|"Positive (AC exceeds BC); Weber central"| C["Normal / symmetric"]
    B -->|"Negative (BC exceeds AC); Weber to SAME ear"| D["Conductive loss"]
    B -->|"Positive; Weber to OPPOSITE ear"| E["Sensorineural loss (worse ear)"]
    B -->|"Negative but Weber to OPPOSITE ear"| F["FALSE-NEGATIVE Rinne — dead ear; confirm with masking"]

The two tests must always be interpreted as a pair. The combination pattern is:

Rinne (Right)	Rinne (Left)	Weber	Diagnosis
Positive	Positive	Central	Normal hearing or symmetric SNHL
Negative	Positive	Lateralises RIGHT	Conductive loss RIGHT
Positive	Negative	Lateralises LEFT	Conductive loss LEFT
Positive	Positive	Lateralises LEFT	SNHL RIGHT
Positive	Positive	Lateralises RIGHT	SNHL LEFT
Negative	Positive	Lateralises LEFT	Beware — false-negative Rinne RIGHT (dead ear right)

That last row is the clinical trap: Rinne negative on the right, Weber lateralises left (the good side) → the right ear is dead, not conductive.

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Absolute Bone Conduction Test (ABC / Schwabach Test)

The ABC test compares the patient’s bone conduction to the examiner’s bone conduction — using the examiner as a normal reference. It is performed with a 256 Hz fork.

Technique

1. Strike the fork and place it on the patient’s mastoid. Ask them to tell you when the sound disappears.
2. Immediately transfer the fork to your own mastoid.
3. Repeat in reverse (start on your mastoid, transfer to the patient’s when you can no longer hear it).

Interpretation

ABC normal (equal to examiner): Patient’s cochlear function is normal or proportionate to the examiner’s — either normal or a conductive loss without cochlear involvement.

ABC reduced (patient loses sound before examiner): Patient’s bone conduction is worse than normal — indicates sensorineural loss.

ABC increased (patient continues to hear after examiner): This should not occur unless the examiner has their own SNHL — a finding that warrants the examiner visiting an audiologist.

The ABC test is limited by examiner variability (the examiner’s own hearing must be known normal) and is largely superseded by audiometry in clinical practice. It remains on MBBS syllabi.

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The Stenger Test — Brief Note

The Stenger test is used when non-organic (functional) hearing loss is suspected — specifically, when a patient claims to have profound unilateral hearing loss that cannot be explained by the clinical findings. Two identical forks are struck simultaneously and placed at equal distance from both ears. By the Stenger principle, a person with normal hearing in both ears will hear only the fork placed closer; a person with true unilateral loss will respond normally; a person pretending deafness will ignore both forks (because acknowledging one would reveal that they can hear). If the patient stops responding when both forks are introduced simultaneously, the test is positive for non-organic hearing loss.

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Key Numbers

Parameter	Value
Standard tuning fork frequency for ENT	512 Hz
Rinne positive (normal result)	AC > BC
Rinne negative (conductive loss)	BC > AC
Conductive loss required for Rinne negative	Approximately ≥20–25 dB
Weber lateralises to poorer ear →	Conductive loss on that side
Weber lateralises to better ear →	SNHL on opposite side
False-negative Rinne occurs when	Ipsilateral profound SNHL (dead ear)
ABC test fork frequency	256 Hz

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Frequently Asked Questions

What is the difference between Rinne-negative and false-negative Rinne? A true Rinne-negative result (BC > AC) with Weber lateralising to the same ear = conductive hearing loss on that side. A false-negative Rinne (BC > AC) with Weber lateralising to the opposite (good) ear = dead ear — profound SNHL on the Rinne-negative side, so severe that air conduction cannot be heard at all, and the bone-conducted fork is perceived by the opposite cochlea via transcranial transmission. The Weber is the rescue test that makes the distinction.

Why does the Weber lateralise to the conductive ear? The conductive ear has an impaired middle ear but an intact cochlea. In normal life, the ambient environmental noise that reaches the cochlea through the intact middle ear provides a masking background. When the middle ear is blocked or impaired, less ambient sound enters the cochlea — the signal-to-noise ratio improves. The bone-conducted tuning fork, arriving directly at the cochlea without passing through the impaired middle ear, faces less masking competition. It therefore appears louder on the conductive side, even though that ear is the “worse” one.

Can tuning fork tests replace an audiogram? No. Tuning fork tests provide bedside classification (conductive vs sensorineural, roughly which side, roughly how severe) but cannot quantify the degree of hearing loss, identify the exact frequency pattern, or reliably detect mild losses. They are screening tools that should always be followed by formal pure-tone audiometry. A negative Rinne requires a threshold of approximately 20–25 dB — losses smaller than this will give a false-positive (Rinne positive) even in the presence of real conductive hearing loss.