What to expect during a bone conduction test

When you’re getting your hearing checked, experts deploy a variety of tests. The process is a bit more involved than simply hearing a beep and raising your hand, as you may remember from childhood. One assessment tactic you may encounter during a hearing clinic visit is a bone conduction test.

Through this test, audiologists evaluate the function of your inner ear and auditory nerve, says Jessica Stiel, AuD, CCC-A, an audiologist with The Ohio State University Wexner Medical Center. The bone conduction test helps identify exactly what part of your ear (middle, outer, or inner) is experiencing hearing loss. This in turn helps pin down what type of hearing loss you have.

Find out more about the bone conduction test, including what to expect when it’s performed and why it’s an important part of your hearing assessment.

What happens during a bone conduction test?

During a bone conduction test, you’ll sit in a soundproof room or booth. You will have just completed the "regular" pure-tone hearing test done with headphones or earphones (aka the air conduction test). The air conduction test measures the quietest sounds a person can hear across different frequencies when the sound travels through the whole sensory organ: from the outer ear, through the middle ear, to the inner ear and finally to the brain. 

The hearing care professional will come into the booth and place a bone oscillator on your skull, Stiel explains. “Usually [it’s] on the mastoid bone behind the ear or on the forehead,” she says. A headband will anchor it in the right spot. By vibrating the mastoid bone, this device directly stimulates your inner ear, bypassing the middle and outer ear.

Stiel notes that once the bone oscillator is in place, sounds will play at different frequencies and volumes, and you’ll indicate what you hear. The tones will sound just like the tones from the air conduction test to you. You will respond in the same manner, by either raising your hand or pushing a button.

Both tests are pain-free and non-invasive. Overall, your hearing assessment may take up to an hour.

What do bone conduction test results reveal?

These two tests—air conduction and bone conduction pure-tone tests—have a lot in common: sounds play, and you’ll signal when you hear them. But despite the similarities, the test results are meaningfully distinct.

“We hear both by air conduction (the sound travels through the air to reach our outer, middle, and inner ear) and by bone conduction (the sound travels through the bones of the skull to reach the inner ear directly without having to pass through the outer and middle ear),” explains Terry Zwolan, PhD, CCC-A, director of audiology access and standard of care at Cochlear Americas.

The air conduction test shows how well you hear those sounds traveling through the whole system, while the bone conduction test examines the hearing organ starting with the inner ear. Together, the tests help hearing professionals pinpoint the cause of the hearing loss and whether it’s due to a problem in the outer or middle ear, or a problem related to the inner ear or auditory nerve.

For instance, you might have fluid in your middle ear, Zwolan says. In that case, “the sounds will need to be louder in order to be heard when they are transmitted through air conduction,” she says.

Conductive hearing loss

If you have hearing loss, but no inner ear issues, your bone conduction tests will be normal, while your air conduction tests will show hearing loss. “If bone conduction thresholds are normal but air conduction thresholds are not, it indicates a conductive hearing loss,” Stiel explains.

Conductive hearing loss, which involves the middle or outer ear, can be temporary or permanent. You could experience this form of hearing loss due to swimmers’ ear or wax buildup, both of which are relatively easy to treat. Other more complex issues may mean permanent hearing loss, and treatment with hearing aids or bone-anchored hearing systems.

Sensorineural hearing loss

“If both air and bone conduction thresholds are abnormal and similar, it suggests sensorineural hearing loss,” Stiel says. Sensorineural hearing loss is the more common type of hearing loss and is always permanent.

If you have this type of hearing loss, you will likely need either hearing aids or cochlear implants. 

Mixed hearing loss

A mixed hearing loss, as the name suggests, is made up of both conductive and sensorineural components. “Occasionally, the audiogram will indicate there is a problem with both air and bone conduction test results, and, in addition, they may note that air conduction signals need to be louder than bone conduction signals to be heard,” Zwolan says. 

A mixed hearing loss may require a treatment for the conductive component as well as one for the sensorineural component. With this type of hearing loss, you may need medication or surgery to treat the outer or middle ear issue, as well as hearing aids to treat the hearing loss attributed to the inner ear.  

Why bone conduction tests are important

Sound travels to your brain through multiple pathways, therefore it requires a battery of tests to fully understand what’s going on. “It is important for an audiologist to test using bone conduction whenever air conduction testing indicates that a hearing loss may be present,” Zwolan says.

If an audiologist solely relies on air conduction testing, they won’t know if the hearing loss is conductive, sensorineural or mixed. The type of hearing loss makes a big difference in determining what's causing the problem.  

Bone conduction testing is an important part of a comprehensive hearing exam because it gives the audiologist or hearing instrument specialist a more complete picture of your hearing ability. And knowing the type of hearing loss you have is “crucial for planning appropriate treatment or management strategies, such as hearing aids or medical intervention,” Stiel says.