Simply put, bone conduction is the process by which we perceive sound through bones in the skull.
Audiologists and Speech-Language Pathologists are very familiar with the concept of bone conduction. We know that if there is loss of hearing through ear canal, bone conduction can still work to perceive sound by bypassing, and standing in for, the tympanic membrane (eardrum).
Bone conduction hearing has huge implications for people with hearing loss, but did you know it can be used with great results for those with normal hearing as well?
How is Bone Conduction Different from Normal Hearing?
First, you’ll need to know a little about the cochlea (ko-klee-uh) (Greek for snail). The cochlea is a snail-shaped structure found in the inner ear that is filled with fluid. When a sound enters the ear through the usual route—the ear canal—the stimulus vibrates the eardrum which then sets into motion fluid in the cochlea. The fluid stimulates tiny hairs which attach to nerves that send the message to the brain for processing. Bone conduction is the way by which we can “cut out the middle man” and send the message directly to the cochlea.
Have you ever heard a recording of your voice and though, “Wow! That doesn’t sound like me!” Well, there’s a reason for that.
When you listen to your own voice, you’re getting the sound stimulus from both your ear canal and bone conduction. This augments the stimulus and changes the way your voice sounds to you. When you hear a recording of your voice, you’re hearing the version of voice that everyone else hears and, you’re hearing it ten times faster than through the ear canal.
Bone Conduction and Ludwig Van Beethoven
Most people know that the pianist composer, Beethoven, had progressive hearing loss from the time he was twenty-six years old. By the time he was forty-four, he had become almost entirely deaf.
There is documentation that talks about how he used bone conduction as a compensatory strategy for his hearing loss. While composing, he would bite down on a rod (such as a pencil) and touch it to the piano sounding board in order to perceive the sounds of the piano through his teeth and bones of the skull. Can you imagine?
Bone Conduction and The Military
Tactical bone conduction headsets were used long before they became readily available to the public. The military used them as way to effectively and discretely communicate with one another without diminishing their situational awareness—the ability to be vigilant to their surroundings.
Bone Conduction and Aural Rehabilitation
Aural rehabilitation—the process of identifying and treating hearing loss—includes methods that use bone conduction as a primary source of auditory stimulation so that people can continue to perceive sound.
Aural rehabilitation can include the use of amplification devices, such as hearing aids that can be placed inside the ear canal or on the bones of the skull (usually attached to the skull directly behind the ear). For people who have hearing loss as a result of damage or malformation of the external ear, bone conduction is a great option.
Why Use Bone Conduction if I have Normal Hearing?
So why would someone with normal hearing want to listen through bone conduction? Here are a few reasons:
- Situational awareness. People who like to exercise outside while listening to music or podcasts and still need to be aware of sounds in their environment for safety.
- Improve the voice for speaking, singing or acting. Many people who are engaging in voice training can benefit from the use of bone conduction to help augment and improve the quality of their expression.
- Comfort. For some people, wearing earphones inside the ears is uncomfortable or not possible. Bone conduction offers a alternate route.
- Protection from amplification and hearing loss. As much as we love our headphones and earbuds, the amplification (volume) is often unregulated and damage can occur with long-time use, even if we don’t notice it right away.
- Speech and occupational therapy. Many people with normal hearing have benefited from the use of bone conduction as an adjunct to Speech-Language Pathology and Occupational Therapy. Implications include attention, concentration, motor control and coordination, and language processing.
Read an interesting article about bone conduction headphones here.
Bone Conduction and Neuroplasticity
Neuroplasticity, or the brain’s ability to change and compensate, was a major discovery in the early 1940s. It changed the way we think about the ability to rehabilitate and “train” our brains. The leading bone conduction headphones manufacturer, Aftershoks®, teamed up with Sound For Life, Ltd., to create the Forbrain® bone conduction headphones. They have been designed to tap into our ability to train our brains by augmenting the frequencies we hear and capitalizing on the brain’s attention centers.
A slight shift in frequencies of the sounds heard through these headphones attracts the attention of your brain just enough to make it work that much harder to process it. Like a muscle, the more it’s challenged, the more the brain grows. And all you have to do is wear them.