What Is Bone Conduction Testing?

Article At a Glance

• Bone conduction testing bypasses much of the outer- and middle-ear sound-conduction pathway by sending vibrations through the skull to stimulate the inner ears.
• Audiologists compare bone-conduction and air-conduction thresholds to help determine whether hearing loss has a conductive component, a sensorineural component, or both.
• The test is non-invasive and generally well tolerated and is commonly performed as part of a comprehensive hearing evaluation when clinically appropriate.
• Results are plotted on an audiogram, where the relationship between air- and bone-conduction thresholds helps the audiologist interpret the type and degree of hearing loss.
• Bone-conduction results are not interpreted alone. Otoscopy, tympanometry, speech testing, symptoms, medical history, masking, and other findings may all affect the final interpretation.

Bone conduction testing is an important part of many comprehensive hearing evaluations because it helps audiologists answer a question that air-conduction testing alone cannot fully resolve: is reduced hearing sensitivity related primarily to sound transmission through the outer or middle ear, the sensorineural auditory system, or a combination of both?

The answer comes from comparing air-conduction thresholds with bone-conduction thresholds rather than treating either measurement as a stand-alone diagnosis.

Bone Conduction Testing Helps Determine the Type of Hearing Loss

When sound reaches the ear through the usual air-conduction pathway, it travels through the ear canal, vibrates the eardrum, moves the small bones of the middle ear, and ultimately stimulates the cochlea.

Air-conduction testing therefore reflects the functioning of the auditory system across this pathway.

Bone-conduction testing takes a different route. A bone oscillator placed against the skull produces vibrations that can stimulate the cochleae while bypassing much of the outer- and middle-ear sound-conduction pathway.

Comparing the two sets of thresholds helps an audiologist determine whether a conductive component is present.

For example, if air-conduction thresholds are poorer than bone-conduction thresholds by a clinically meaningful amount, the pattern may indicate that the outer or middle ear is contributing to the hearing loss.

If both air- and bone-conduction thresholds are reduced without a clinically meaningful air-bone gap, the pattern is more consistent with sensorineural hearing loss.

These findings classify the hearing-loss pattern, but they do not necessarily identify its exact medical cause.

What Is Bone Conduction Testing?

Bone conduction testing is a form of pure-tone audiometry.

Instead of presenting tones through insert earphones or headphones, the audiologist uses a device called a bone oscillator or bone vibrator. It is commonly positioned on the mastoid portion of the skull behind the ear, although other placements may be used in particular testing situations.

The oscillator produces vibrations at selected frequencies and intensity levels.

Those vibrations travel through the skull and can stimulate the cochleae. The patient responds when a tone is heard, allowing the audiologist to estimate the lowest level detected at each tested frequency.

An important limitation is that bone-conducted vibration can reach both cochleae. The response cannot automatically be assumed to come only from the ear beside the oscillator.

When ear-specific bone-conduction information is needed, the audiologist may use masking noise in the non-test ear.

The Three Major Hearing-Loss Patterns

Comparing air- and bone-conduction thresholds can help classify hearing loss into three broad categories.

Conductive Hearing Loss

Conductive hearing loss occurs when sound transmission through the outer or middle ear is reduced while cochlear sensitivity is comparatively better.

The audiogram typically shows bone-conduction thresholds that are better than air-conduction thresholds, creating an air-bone gap.

Possible causes include:

• Earwax obstructing the ear canal
• Middle-ear fluid
• Some ear infections
• Tympanic membrane abnormalities
• Ossicular-chain disorders
• Otosclerosis
• Other outer- or middle-ear conditions

The audiogram identifies a conductive pattern; determining the specific cause may require otoscopy, tympanometry, medical examination, imaging, or other evaluation.

Sensorineural Hearing Loss

Sensorineural hearing loss generally produces reduced air- and bone-conduction thresholds without a clinically meaningful conductive gap.

This pattern reflects reduced sensitivity within the sensorineural auditory system and is commonly associated with cochlear hearing loss.

Possible contributors include aging, noise exposure, genetic factors, certain medications, infections, and many other conditions.

Pure-tone bone-conduction testing alone generally cannot determine the exact underlying cause or distinguish every cochlear disorder from every neural disorder.

Mixed Hearing Loss

Mixed hearing loss includes both conductive and sensorineural components.

In this pattern, bone-conduction thresholds are reduced, but air-conduction thresholds are poorer by a clinically meaningful amount.

This means there is evidence of sensorineural hearing loss along with an additional outer- or middle-ear contribution.

Bone Conduction vs. Air Conduction Testing

Air- and bone-conduction testing complement one another.

Feature	Air Conduction	Bone Conduction
How sound is presented	Insert earphones or headphones	Bone oscillator placed against the skull
Outer and middle ear involved?	Yes	Largely bypassed
Primary clinical role	Measures hearing sensitivity through the usual auditory pathway	Helps determine whether a conductive component is present
Ear-specific without additional measures?	Generally yes with appropriate earphones	Not always; masking may be required
Interpreted alone?	No	No

 

The difference between air- and bone-conduction thresholds at the same frequency is called an air-bone gap.

A meaningful air-bone gap can support the presence of a conductive component, but interpretation is not based on one universal number in isolation. Audiologists consider the size and consistency of the gap, test frequency, masking, equipment and transducer characteristics, reliability of the responses, and the rest of the audiological findings.

What Happens During a Bone Conduction Test?

Bone conduction testing may be performed during a comprehensive hearing evaluation after air-conduction thresholds have been measured or whenever the audiologist needs additional information about the type of hearing loss.

The process commonly includes the following:

1. The bone oscillator is positioned. It is usually held against the mastoid area behind the ear with a headband.
2. Pure tones are presented. The audiologist tests selected frequencies that are appropriate for the evaluation and the capabilities of the bone-conduction transducer.
3. You respond when you hear a tone. Adults may press a button or raise a hand. Children may use conditioned play or another age-appropriate behavioral response.
4. The audiologist determines thresholds. The level of each tone is adjusted to estimate the softest sound you can reliably detect.
5. Masking may be used. Noise may be presented to the opposite ear when necessary to obtain ear-specific information.
6. Results are compared with air-conduction thresholds. The relationship between the two helps determine the hearing-loss pattern.

The test is non-invasive. Some people notice pressure from the headband or feel vibration from lower-frequency stimuli, but the procedure is generally well tolerated.

The time required varies according to the number of frequencies tested, whether masking is needed, the patient’s age and responses, and the complexity of the hearing loss.

Why Masking Matters in Bone Conduction Testing

One of the most important concepts in bone-conduction audiometry is that skull vibration can stimulate both inner ears.

This means an unmasked bone-conduction threshold may represent the response of the better cochlea rather than the cochlea on the side where the oscillator is positioned.

When the audiologist needs to know the bone-conduction threshold of a particular ear, masking noise can be delivered to the non-test ear.

The purpose is to keep that ear from responding to the test signal so the clinician can obtain more reliable ear-specific information.

Masking decisions follow established audiological principles and depend on the air- and bone-conduction results, transducers, frequencies, and other test conditions.

How Bone Conduction Results Appear on an Audiogram

An audiogram displays hearing thresholds across different frequencies.

The horizontal axis represents frequency, measured in hertz (Hz), with lower-pitched frequencies toward the left and higher-pitched frequencies toward the right.

The vertical axis represents hearing level in decibels hearing level (dB HL). Softer levels appear near the top and louder levels farther down the graph.

Different symbols distinguish air-conduction and bone-conduction results as well as masked and unmasked measurements.

Common audiometric notation may include:

• O for unmasked right-ear air conduction
• X for unmasked left-ear air conduction
• < and > for certain unmasked bone-conduction measurements
• Different bracket symbols for masked bone-conduction thresholds

Exact notation can vary, so patients should ask their audiologist to explain the symbols on their own audiogram.

Understanding the Air-Bone Gap

The air-bone gap is the difference between air- and bone-conduction thresholds at a given frequency.

A consistent, clinically meaningful gap can indicate a conductive component.

However, audiograms have normal test-retest variability, and small differences between air and bone thresholds can occur for technical or statistical reasons.

For that reason, an audiologist does not diagnose conductive hearing loss from one isolated difference on the graph.

The clinician evaluates the overall pattern and may compare it with:

• Otoscopy
• Tympanometry
• Acoustic reflexes
• Speech testing
• Symptoms and medical history
• Previous audiograms
• Other diagnostic findings when indicated

What Is Considered a Normal Bone Conduction Threshold?

Hearing thresholds are expressed in dB HL, a clinical scale referenced to standardized hearing levels.

In many adult clinical settings, thresholds around 0 to 25 dB HL are broadly considered within a conventional normal or near-normal range, although classification systems vary.

For children, some clinicians use more stringent criteria because even relatively small hearing deficits can be important for speech, language, and learning.

Degree-of-hearing-loss labels also vary somewhat among professional systems. Categories such as mild, moderate, severe, and profound are useful descriptions, but the boundaries should not be treated as universal biological cutoffs.

More importantly, a bone-conduction threshold does not by itself establish that the entire cochlea, auditory nerve, and central auditory pathway are functioning normally.

Pure-tone audiometry measures behavioral detection of tones. Other tests may be required when the clinical question involves cochlear function, auditory-nerve function, speech processing, or neurological disease.

Who May Need Bone Conduction Testing?

Bone conduction testing is commonly used when an audiologist needs to determine the type of hearing loss.

It may be appropriate when:

• Air-conduction testing identifies reduced hearing sensitivity
• A conductive component is suspected
• Tympanometry or otoscopy suggests outer- or middle-ear dysfunction
• Hearing differs between the ears
• A person has a history of ear disease or ear surgery
• A child is being evaluated for possible hearing loss
• Hearing technology or medical management is being considered and the type of hearing loss needs clarification

The specific test battery depends on the patient’s age, symptoms, medical history, and the clinical question.

A failed screening does not necessarily mean every person will undergo exactly the same diagnostic tests.

Bone Conduction Testing in Children

Bone conduction testing can be used in pediatric audiology when developmentally appropriate and clinically necessary.

For children able to participate in conditioned play audiometry, the child may perform a simple activity whenever a tone is heard.

Infants and younger children may require other behavioral or objective hearing tests depending on their developmental level.

Determining whether hearing loss has a conductive component is particularly important in children because middle-ear conditions are common and fluctuating hearing can affect access to speech and language.

However, the developmental impact of hearing loss varies considerably among children. Early identification and appropriate follow-up can help families and clinicians determine whether medical care, hearing support, communication intervention, monitoring, or other services are needed.

Bone Conduction Testing and Tinnitus

Bone conduction testing does not detect or measure tinnitus itself.

Tinnitus is the perception of sound without a corresponding external acoustic source, and its presence is determined from the person’s reported experience.

Audiometry is often included in a tinnitus evaluation because hearing loss frequently accompanies tinnitus.

Bone- and air-conduction testing can identify whether a measurable hearing loss is conductive, sensorineural, or mixed, which may provide useful clinical context.

However, an audiogram usually cannot determine exactly why an individual has tinnitus, and the configuration of hearing loss does not reliably reveal the perceived pitch, loudness, severity, or cause of tinnitus.

Learn more in our Tinnitus: The Complete Guide.

Bone Conduction Results Help Guide the Next Step

Bone conduction testing helps classify hearing loss, but treatment depends on the underlying cause, severity, symptoms, medical findings, communication needs, and individual circumstances.

A conductive pattern may lead to additional examination for an outer- or middle-ear cause.

Some conductive conditions are temporary or medically treatable. Others may require monitoring, surgery, hearing technology, or another management strategy.

Sensorineural hearing loss may lead to discussion of hearing aids, assistive listening technology, communication strategies, cochlear implant evaluation in appropriate cases, medical assessment, or monitoring.

Mixed hearing loss may require a combination of medical and audiological management.

The audiogram helps identify the hearing-loss pattern. It does not, by itself, prescribe the treatment.

When Hearing Changes Need Prompt Medical Attention

Not every hearing change should wait for a routine hearing appointment.

Sudden hearing loss or a rapid unexplained change in hearing warrants prompt medical evaluation, particularly when it develops over hours or a few days.

Other symptoms that may justify timely or urgent evaluation include significant ear pain or drainage, new neurological symptoms, major head injury, or other concerning changes.

Read more about hearing-loss symptoms that may require prompt medical attention.

Frequently Asked Questions

Is a Bone Conduction Test Painful?

Bone conduction testing is non-invasive and is generally well tolerated.

The oscillator is held against the skull by a headband. Some people notice pressure from the headband or vibration during lower-frequency tones.

Tell the audiologist if you experience discomfort so the equipment and testing procedure can be checked.

How Long Does Bone Conduction Testing Take?

There is no universal testing time.

The duration depends on how many frequencies need to be measured, whether one or both ears require masked thresholds, the person’s response consistency, age, and the complexity of the hearing loss.

Bone conduction is usually one part of a broader hearing evaluation.

Can Children Have Bone Conduction Testing?

Yes.

Children who are developmentally able to participate in behavioral hearing testing can often complete bone-conduction measurements using standard or play-based response methods.

Audiologists may use different procedures for infants and very young children who cannot provide reliable behavioral responses.

Does Bone Conduction Testing Require a Referral?

Requirements vary.

Access to audiological services can depend on location, age, insurance or payer requirements, healthcare system policies, and the type of service being requested.

A physician referral therefore should not be assumed to be either universally required or universally unnecessary.

If an audiological evaluation identifies findings that may require medical diagnosis or treatment, the audiologist may recommend evaluation by an otolaryngologist or another appropriate healthcare professional.

Does Normal Bone Conduction Rule Out Hearing Problems?

No.

Normal or near-normal bone-conduction thresholds can help show that cochlear sensitivity is sufficient to detect the tested tones through bone conduction, but they do not rule out every hearing or auditory disorder.

A person can have difficulty with speech in noise, auditory processing, tinnitus, fluctuating symptoms, or other problems that are not fully described by bone-conduction thresholds.

The entire audiological and medical picture matters.

Can Bone Conduction Testing Diagnose the Cause of Hearing Loss?

Not usually by itself.

Bone conduction is particularly valuable for determining whether a conductive component is present.

The exact cause may require otoscopy, tympanometry, additional audiological testing, medical examination, laboratory evaluation, imaging, or other testing depending on the circumstances.

What Happens After an Abnormal Bone Conduction Result?

The next step depends on the complete pattern.

Reduced bone-conduction thresholds may support a sensorineural component, but the audiologist will interpret them alongside air-conduction thresholds, masking, speech testing, middle-ear findings, symptoms, and medical history.

A significant air-bone gap may support a conductive component and can lead to additional evaluation of the outer or middle ear.

Neither pattern automatically determines one treatment.

The Bottom Line

Bone conduction testing is an important component of diagnostic audiometry because it helps audiologists distinguish conductive, sensorineural, and mixed patterns of hearing loss.

Its greatest value comes from comparison with air-conduction thresholds.

Because bone-conducted sound can stimulate both cochleae, masking may be necessary to obtain ear-specific information. Small air-bone differences also require professional interpretation rather than being treated as automatic evidence of disease.

Most importantly, a bone-conduction audiogram identifies a hearing-loss pattern—not necessarily the exact medical cause.

Your audiologist can explain how the results fit with your air-conduction thresholds, tympanometry, speech testing, symptoms, medical history, and any additional evaluation that may be appropriate.